Groups > linux.kernel > #1220282 > unrolled thread

[PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

Started by	Julien Grall <julien.grall@citrix.com>
First post	2015-09-07 17:40 +0200
Last post	2015-09-15 15:30 +0200
Articles	20 on this page of 27 — 6 participants

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  [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:40 +0200
    [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:40 +0200
      Re: [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity  is the same for Xen and Linux Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-07 18:50 +0200
    [PATCH v4 15/20] block/xen-blkfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
    [PATCH v4 20/20] arm/xen: Add support for 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
    [PATCH v4 17/20] net/xen-netfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
    [PATCH v4 10/20] xen/xenbus: Use Xen page definition Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
    [PATCH v4 16/20] block/xen-blkback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
    [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
      Re: [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page  granularity Wei Liu <wei.liu2@citrix.com> - 2015-09-07 19:00 +0200
        Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on  64KB page granularity Wei Liu <wei.liu2@citrix.com> - 2015-09-08 13:10 +0200
        Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running  on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-08 13:10 +0200
    Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB  page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-11 21:50 +0200
    Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 11:00 +0200
      Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 12:50 +0200
        Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 13:10 +0200
          Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 13:30 +0200
            Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 14:10 +0200
              Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 14:50 +0200
                Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 16:40 +0200
                  Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 16:50 +0200
                  Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-14 17:00 +0200
                    Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 17:30 +0200
              Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-18 16:20 +0200
          Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Arnd Bergmann <arnd@arndb.de> - 2015-09-14 13:40 +0200
            Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB  page in Linux David Vrabel <david.vrabel@citrix.com> - 2015-09-15 15:20 +0200
              Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Arnd Bergmann <arnd@arndb.de> - 2015-09-15 15:30 +0200

Page 1 of 2 [1] 2 Next page →

#1220282 — [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:40 +0200
Subject	[PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux
Message-ID	<q66Gt-1eb-3@gated-at.bofh.it>

Hi all,

ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
hypercall interface and PV protocol are always based on 4KB page granularity.

Any attempt to boot a Linux guest with 64KB pages enabled will result to a
guest crash.

This series is a first attempt to allow those Linux running with the current
hypercall interface and PV protocol.

This solution has been chosen because we want to run Linux 64KB in released
Xen ARM version or/and platform using an old version of Linux DOM0.

There is room for improvement, such as support of 64KB grant, modification
of PV protocol to support different page size... They will be explored in a
separate patch series later.

TODO list:
    - Convert swiotlb to 64KB
    - Convert xenfb to 64KB
    - Support for multiple page ring support
    - Support for 64KB in gnttdev
    - Support of non-indirect grant with 64KB frontend
    - It may be possible to move some common define between
    netback/netfront and blkfront/blkback in an header

I've got most of the patches for the TODO items. I'm planning to send them as
a follow-up as it's not a requirement for a basic guests.

All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
to run it on x86 as I don't have a box with Xen x86 running. I would be
happy if someone give a try and see possible regression for x86.

I know that Konrad as a test-suite for x86. Konrand, would it be possible to
give a run to for this series?

A branch based on the latest xentip/for-linus-4.3 can be found here:

git://xenbits.xen.org/people/julieng/linux-arm.git branch xen-64k-v4

Comments, suggestions are welcomed.

Sincerely yours,

Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: boris.ostrovsky@oracle.com
Cc: wei.liu2@citrix.com
Cc: roger.pau@citrix.com

Status of each patch:

A: Reviewed-by - Acked-by
M: Patch modified in this series
m: Minor changes in this series (i.e renaming due to previous patches, typoes)
L: Missing Acked-by from a Linux maintainers (Boris, David, Konrad)
N: Missing Acked-by from a Netback maintainers (Ian or Wei)

Julien Grall (20):
A       net/xen-netback: xenvif_gop_frag_copy: move GSO check out of the loop
A       arm/xen: Drop pte_mfn and mfn_pte
A M L   xen: Add Xen specific page definition
A M     xen/grant: Introduce helpers to split a page into grant
A       xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one
A       block/xen-blkfront: Split blkif_queue_request in 2
A m     block/xen-blkfront: Store a page rather a pfn in the grant structure
A       block/xen-blkfront: split get_grant in 2
A m L   xen/biomerge: Don't allow biovec's to be merged when Linux is not
          using 4KB pages
A       xen/xenbus: Use Xen page definition
A m L   tty/hvc: xen: Use xen page definition
  M L   xen/balloon: Don't rely on the page granularity is the same for Xen
          and Linux
A       xen/events: fifo: Make it running on 64KB granularity
A       xen/grant-table: Make it running on 64KB granularity
A m     block/xen-blkfront: Make it running on 64KB page granularity
A       block/xen-blkback: Make it running on 64KB page granularity
A m     net/xen-netfront: Make it running on 64KB page granularity
  m  N  net/xen-netback: Make it running on 64KB page granularity
A m     xen/privcmd: Add support for Linux 64KB page granularity
A       arm/xen: Add support for 64KB page granularity

 arch/arm/include/asm/xen/page.h     |  18 +-
 arch/arm/xen/enlighten.c            |   6 +-
 arch/arm/xen/p2m.c                  |   6 +-
 arch/x86/include/asm/xen/page.h     |   2 +-
 drivers/block/xen-blkback/blkback.c |   5 +-
 drivers/block/xen-blkback/common.h  |  17 +-
 drivers/block/xen-blkback/xenbus.c  |   9 +-
 drivers/block/xen-blkfront.c        | 552 +++++++++++++++++++++++-------------
 drivers/net/xen-netback/common.h    |  18 +-
 drivers/net/xen-netback/netback.c   | 163 +++++++----
 drivers/net/xen-netfront.c          | 122 +++++---
 drivers/tty/hvc/hvc_xen.c           |   4 +-
 drivers/xen/balloon.c               |  59 +++-
 drivers/xen/biomerge.c              |   8 +
 drivers/xen/events/events_base.c    |   2 +-
 drivers/xen/events/events_fifo.c    |   2 +-
 drivers/xen/grant-table.c           |  32 ++-
 drivers/xen/privcmd.c               |   8 +-
 drivers/xen/xenbus/xenbus_client.c  |   6 +-
 drivers/xen/xenbus/xenbus_probe.c   |   3 +-
 drivers/xen/xlate_mmu.c             | 124 +++++---
 include/xen/grant_table.h           |  51 ++++
 include/xen/page.h                  |  27 +-
 23 files changed, 855 insertions(+), 389 deletions(-)

-- 
2.1.4

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#1220283 — [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:40 +0200
Subject	[PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux
Message-ID	<q66Gv-1eb-43@gated-at.bofh.it>
In reply to	#1220282

For ARM64 guests, Linux is able to support either 64K or 4K page
granularity. Although, the hypercall interface is always based on 4K
page granularity.

With 64K page granularity, a single page will be spread over multiple
Xen frame.

To avoid splitting the page into 4K frame, take advantage of the
extent_order field to directly allocate/free chunk of the Linux page
size.

Note that PVMMU is only used for PV guest (which is x86) and the page
granularity is always 4KB. Some BUILD_BUG_ON has been added to ensure
that because the code has not been modified.

Signed-off-by: Julien Grall <julien.grall@citrix.com>

---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>

Note that two BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE) in code built
for the PV MMU code is kept in order to have at least one even if we
ever decide to drop of code section.

    Changes in v4:
        - s/xen_page_to_pfn/page_to_xen_pfn/ based on the new naming
        - Use the field lru in the page to get a list of pages when
        decreasing the memory reservation. It avoids to use a static
        array to store the pages (see v3).
        - Update comment for EXTENT_ORDER.

    Changes in v3:
        - Fix errors reported by checkpatch.pl
        - s/mfn/gfn/ based on the new naming
        - Rather than splitting the page into 4KB chunk, use the
        extent_order field to allocate directly a Linux page size. This
        is avoid lots of code for no benefits.

    Changes in v2:
        - Use xen_apply_to_page to split a page in 4K chunk
        - It's not necessary to have a smaller frame list. Re-use
        PAGE_SIZE
        - Convert reserve_additional_memory to use XEN_... macro
---
 drivers/xen/balloon.c | 59 ++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 44 insertions(+), 15 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index c79329f..3babf13 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -70,6 +70,11 @@
 #include <xen/features.h>
 #include <xen/page.h>
 
+/* Use one extent per PAGE_SIZE to avoid to break down the page into
+ * multiple frame.
+ */
+#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
+
 /*
  * balloon_process() state:
  *
@@ -230,6 +235,11 @@ static enum bp_state reserve_additional_memory(long credit)
 	nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
 
 #ifdef CONFIG_XEN_HAVE_PVMMU
+	/* We don't support PV MMU when Linux and Xen is using
+	 * different page granularity.
+	 */
+	BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
         /*
          * add_memory() will build page tables for the new memory so
          * the p2m must contain invalid entries so the correct
@@ -326,11 +336,11 @@ static enum bp_state reserve_additional_memory(long credit)
 static enum bp_state increase_reservation(unsigned long nr_pages)
 {
 	int rc;
-	unsigned long  pfn, i;
+	unsigned long i;
 	struct page   *page;
 	struct xen_memory_reservation reservation = {
 		.address_bits = 0,
-		.extent_order = 0,
+		.extent_order = EXTENT_ORDER,
 		.domid        = DOMID_SELF
 	};
 
@@ -352,7 +362,11 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 			nr_pages = i;
 			break;
 		}
-		frame_list[i] = page_to_pfn(page);
+
+		/* XENMEM_populate_physmap requires a PFN based on Xen
+		 * granularity.
+		 */
+		frame_list[i] = page_to_xen_pfn(page);
 		page = balloon_next_page(page);
 	}
 
@@ -366,10 +380,15 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 		page = balloon_retrieve(false);
 		BUG_ON(page == NULL);
 
-		pfn = page_to_pfn(page);
-
 #ifdef CONFIG_XEN_HAVE_PVMMU
+		/* We don't support PV MMU when Linux and Xen is using
+		 * different page granularity.
+		 */
+		BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
 		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+			unsigned long pfn = page_to_pfn(page);
+
 			set_phys_to_machine(pfn, frame_list[i]);
 
 			/* Link back into the page tables if not highmem. */
@@ -396,14 +415,15 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 {
 	enum bp_state state = BP_DONE;
-	unsigned long  pfn, i;
-	struct page   *page;
+	unsigned long i;
+	struct page *page, *tmp;
 	int ret;
 	struct xen_memory_reservation reservation = {
 		.address_bits = 0,
-		.extent_order = 0,
+		.extent_order = EXTENT_ORDER,
 		.domid        = DOMID_SELF
 	};
+	LIST_HEAD(pages);
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 	if (balloon_stats.hotplug_pages) {
@@ -425,8 +445,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 			break;
 		}
 		scrub_page(page);
-
-		frame_list[i] = page_to_pfn(page);
+		list_add(&page->lru, &pages);
 	}
 
 	/*
@@ -438,14 +457,23 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 	 */
 	kmap_flush_unused();
 
-	/* Update direct mapping, invalidate P2M, and add to balloon. */
-	for (i = 0; i < nr_pages; i++) {
-		pfn = frame_list[i];
-		frame_list[i] = pfn_to_gfn(pfn);
-		page = pfn_to_page(pfn);
+	/*
+	 * Setup the frame, update direct mapping, invalidate P2M,
+	 * and add to balloon.
+	 */
+	list_for_each_entry_safe(page, tmp, &pages, lru) {
+		/* XENMEM_decrease_reservation requires a GFN */
+		frame_list[i] = xen_page_to_gfn(page);
 
 #ifdef CONFIG_XEN_HAVE_PVMMU
+		/* We don't support PV MMU when Linux and Xen is using
+		 * different page granularity.
+		 */
+		BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
 		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+			unsigned long pfn = page_to_pfn(page);
+
 			if (!PageHighMem(page)) {
 				ret = HYPERVISOR_update_va_mapping(
 						(unsigned long)__va(pfn << PAGE_SHIFT),
@@ -455,6 +483,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 			__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 		}
 #endif
+		list_del(&page->lru);
 
 		balloon_append(page);
 	}
-- 
2.1.4

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#1220330 — Re: [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux

From	Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Date	2015-09-07 18:50 +0200
Subject	Re: [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux
Message-ID	<q67Me-2Kt-13@gated-at.bofh.it>
In reply to	#1220283

On Mon, 7 Sep 2015, Julien Grall wrote:
> For ARM64 guests, Linux is able to support either 64K or 4K page
> granularity. Although, the hypercall interface is always based on 4K
> page granularity.
> 
> With 64K page granularity, a single page will be spread over multiple
> Xen frame.
> 
> To avoid splitting the page into 4K frame, take advantage of the
> extent_order field to directly allocate/free chunk of the Linux page
> size.
> 
> Note that PVMMU is only used for PV guest (which is x86) and the page
> granularity is always 4KB. Some BUILD_BUG_ON has been added to ensure
> that because the code has not been modified.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>

Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>


> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>
> 
> Note that two BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE) in code built
> for the PV MMU code is kept in order to have at least one even if we
> ever decide to drop of code section.
> 
>     Changes in v4:
>         - s/xen_page_to_pfn/page_to_xen_pfn/ based on the new naming
>         - Use the field lru in the page to get a list of pages when
>         decreasing the memory reservation. It avoids to use a static
>         array to store the pages (see v3).
>         - Update comment for EXTENT_ORDER.
> 
>     Changes in v3:
>         - Fix errors reported by checkpatch.pl
>         - s/mfn/gfn/ based on the new naming
>         - Rather than splitting the page into 4KB chunk, use the
>         extent_order field to allocate directly a Linux page size. This
>         is avoid lots of code for no benefits.
> 
>     Changes in v2:
>         - Use xen_apply_to_page to split a page in 4K chunk
>         - It's not necessary to have a smaller frame list. Re-use
>         PAGE_SIZE
>         - Convert reserve_additional_memory to use XEN_... macro
> ---
>  drivers/xen/balloon.c | 59 ++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 44 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index c79329f..3babf13 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -70,6 +70,11 @@
>  #include <xen/features.h>
>  #include <xen/page.h>
>  
> +/* Use one extent per PAGE_SIZE to avoid to break down the page into
> + * multiple frame.
> + */
> +#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
> +
>  /*
>   * balloon_process() state:
>   *
> @@ -230,6 +235,11 @@ static enum bp_state reserve_additional_memory(long credit)
>  	nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
>  
>  #ifdef CONFIG_XEN_HAVE_PVMMU
> +	/* We don't support PV MMU when Linux and Xen is using
> +	 * different page granularity.
> +	 */
> +	BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
> +
>          /*
>           * add_memory() will build page tables for the new memory so
>           * the p2m must contain invalid entries so the correct
> @@ -326,11 +336,11 @@ static enum bp_state reserve_additional_memory(long credit)
>  static enum bp_state increase_reservation(unsigned long nr_pages)
>  {
>  	int rc;
> -	unsigned long  pfn, i;
> +	unsigned long i;
>  	struct page   *page;
>  	struct xen_memory_reservation reservation = {
>  		.address_bits = 0,
> -		.extent_order = 0,
> +		.extent_order = EXTENT_ORDER,
>  		.domid        = DOMID_SELF
>  	};
>  
> @@ -352,7 +362,11 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
>  			nr_pages = i;
>  			break;
>  		}
> -		frame_list[i] = page_to_pfn(page);
> +
> +		/* XENMEM_populate_physmap requires a PFN based on Xen
> +		 * granularity.
> +		 */
> +		frame_list[i] = page_to_xen_pfn(page);
>  		page = balloon_next_page(page);
>  	}
>  
> @@ -366,10 +380,15 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
>  		page = balloon_retrieve(false);
>  		BUG_ON(page == NULL);
>  
> -		pfn = page_to_pfn(page);
> -
>  #ifdef CONFIG_XEN_HAVE_PVMMU
> +		/* We don't support PV MMU when Linux and Xen is using
> +		 * different page granularity.
> +		 */
> +		BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
> +
>  		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> +			unsigned long pfn = page_to_pfn(page);
> +
>  			set_phys_to_machine(pfn, frame_list[i]);
>  
>  			/* Link back into the page tables if not highmem. */
> @@ -396,14 +415,15 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
>  static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
>  {
>  	enum bp_state state = BP_DONE;
> -	unsigned long  pfn, i;
> -	struct page   *page;
> +	unsigned long i;
> +	struct page *page, *tmp;
>  	int ret;
>  	struct xen_memory_reservation reservation = {
>  		.address_bits = 0,
> -		.extent_order = 0,
> +		.extent_order = EXTENT_ORDER,
>  		.domid        = DOMID_SELF
>  	};
> +	LIST_HEAD(pages);
>  
>  #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
>  	if (balloon_stats.hotplug_pages) {
> @@ -425,8 +445,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
>  			break;
>  		}
>  		scrub_page(page);
> -
> -		frame_list[i] = page_to_pfn(page);
> +		list_add(&page->lru, &pages);
>  	}
>  
>  	/*
> @@ -438,14 +457,23 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
>  	 */
>  	kmap_flush_unused();
>  
> -	/* Update direct mapping, invalidate P2M, and add to balloon. */
> -	for (i = 0; i < nr_pages; i++) {
> -		pfn = frame_list[i];
> -		frame_list[i] = pfn_to_gfn(pfn);
> -		page = pfn_to_page(pfn);
> +	/*
> +	 * Setup the frame, update direct mapping, invalidate P2M,
> +	 * and add to balloon.
> +	 */
> +	list_for_each_entry_safe(page, tmp, &pages, lru) {
> +		/* XENMEM_decrease_reservation requires a GFN */
> +		frame_list[i] = xen_page_to_gfn(page);
>  
>  #ifdef CONFIG_XEN_HAVE_PVMMU
> +		/* We don't support PV MMU when Linux and Xen is using
> +		 * different page granularity.
> +		 */
> +		BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
> +
>  		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> +			unsigned long pfn = page_to_pfn(page);
> +
>  			if (!PageHighMem(page)) {
>  				ret = HYPERVISOR_update_va_mapping(
>  						(unsigned long)__va(pfn << PAGE_SHIFT),
> @@ -455,6 +483,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
>  			__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
>  		}
>  #endif
> +		list_del(&page->lru);
>  
>  		balloon_append(page);
>  	}
> -- 
> 2.1.4
> 
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#1220288 — [PATCH v4 15/20] block/xen-blkfront: Make it running on 64KB page granularity

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:50 +0200
Subject	[PATCH v4 15/20] block/xen-blkfront: Make it running on 64KB page granularity
Message-ID	<q66Qa-1px-23@gated-at.bofh.it>
In reply to	#1220282

The PV block protocol is using 4KB page granularity. The goal of this
patch is to allow a Linux using 64KB page granularity using block
device on a non-modified Xen.

The block API is using segment which should at least be the size of a
Linux page. Therefore, the driver will have to break the page in chunk
of 4K before giving the page to the backend.

When breaking a 64KB segment in 4KB chunks, it is possible that some
chunks are empty. As the PV protocol always require to have data in the
chunk, we have to count the number of Xen page which will be in use and
avoid sending empty chunks.

Note that, a pre-defined number of grants are reserved before preparing
the request. This pre-defined number is based on the number and the
maximum size of the segments. If each segment contains a very small
amount of data, the driver may reserve too many grants (16 grants is
reserved per segment with 64KB page granularity).

Furthermore, in the case of persistent grants we allocate one Linux page
per grant although only the first 4KB of the page will be effectively
in use. This could be improved by sharing the page with multiple grants.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>

Improvement such as support 64KB grant is not taken into consideration in
this patch because we have the requirement to run a Linux using 64KB page
on a non-modified Xen.

    Changes in v4:
        - Rebase after d50babbe300eedf33ea5b00a12c5df3a05bd96c7 "
        xen-blkfront: introduce blkfront_gather_backend_features()"
        - Fix typoes
        - Add Roger's acked-by

    Changes in v3:
        - Use DIV_ROUND_UP in INDIRECT_GREFS
        - Split lines over 80 characters whenever it's possible
        - s/mfn/gfn/ based on the new naming
        - The grant callback doesn't allow anymore to change the len
        (wasn't used here).
        - gnttab_foreach_grant has been renamed to gnttab_foreach_grant_in_range
        - Use gnttab_count_grant to get the number of grants in a sg
        - Do some renaming to use the correct variable every time

    Changes in v2:
        - Use gnttab_foreach_grant to split a Linux page into grant
---
 drivers/block/xen-blkfront.c | 324 ++++++++++++++++++++++++++++---------------
 1 file changed, 213 insertions(+), 111 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 4232cbd..f2cdc73 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -78,6 +78,7 @@ struct blk_shadow {
 	struct grant **grants_used;
 	struct grant **indirect_grants;
 	struct scatterlist *sg;
+	unsigned int num_sg;
 };
 
 struct split_bio {
@@ -107,8 +108,12 @@ static unsigned int xen_blkif_max_ring_order;
 module_param_named(max_ring_page_order, xen_blkif_max_ring_order, int, S_IRUGO);
 MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the shared ring");
 
-#define BLK_RING_SIZE(info) __CONST_RING_SIZE(blkif, PAGE_SIZE * (info)->nr_ring_pages)
-#define BLK_MAX_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE * XENBUS_MAX_RING_PAGES)
+#define BLK_RING_SIZE(info)	\
+	__CONST_RING_SIZE(blkif, XEN_PAGE_SIZE * (info)->nr_ring_pages)
+
+#define BLK_MAX_RING_SIZE	\
+	__CONST_RING_SIZE(blkif, XEN_PAGE_SIZE * XENBUS_MAX_RING_PAGES)
+
 /*
  * ring-ref%i i=(-1UL) would take 11 characters + 'ring-ref' is 8, so 19
  * characters are enough. Define to 20 to keep consist with backend.
@@ -147,6 +152,7 @@ struct blkfront_info
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
 	unsigned int feature_persistent:1;
+	/* Number of 4KB segments handled */
 	unsigned int max_indirect_segments;
 	int is_ready;
 	struct blk_mq_tag_set tag_set;
@@ -175,10 +181,23 @@ static DEFINE_SPINLOCK(minor_lock);
 
 #define DEV_NAME	"xvd"	/* name in /dev */
 
-#define SEGS_PER_INDIRECT_FRAME \
-	(PAGE_SIZE/sizeof(struct blkif_request_segment))
-#define INDIRECT_GREFS(_segs) \
-	((_segs + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
+/*
+ * Grants are always the same size as a Xen page (i.e 4KB).
+ * A physical segment is always the same size as a Linux page.
+ * Number of grants per physical segment
+ */
+#define GRANTS_PER_PSEG	(PAGE_SIZE / XEN_PAGE_SIZE)
+
+#define GRANTS_PER_INDIRECT_FRAME \
+	(XEN_PAGE_SIZE / sizeof(struct blkif_request_segment))
+
+#define PSEGS_PER_INDIRECT_FRAME	\
+	(GRANTS_INDIRECT_FRAME / GRANTS_PSEGS)
+
+#define INDIRECT_GREFS(_grants)		\
+	DIV_ROUND_UP(_grants, GRANTS_PER_INDIRECT_FRAME)
+
+#define GREFS(_psegs)	((_psegs) * GRANTS_PER_PSEG)
 
 static int blkfront_setup_indirect(struct blkfront_info *info);
 static int blkfront_gather_backend_features(struct blkfront_info *info);
@@ -466,14 +485,100 @@ static int blkif_queue_discard_req(struct request *req)
 	return 0;
 }
 
+struct setup_rw_req {
+	unsigned int grant_idx;
+	struct blkif_request_segment *segments;
+	struct blkfront_info *info;
+	struct blkif_request *ring_req;
+	grant_ref_t gref_head;
+	unsigned int id;
+	/* Only used when persistent grant is used and it's a read request */
+	bool need_copy;
+	unsigned int bvec_off;
+	char *bvec_data;
+};
+
+static void blkif_setup_rw_req_grant(unsigned long gfn, unsigned int offset,
+				     unsigned int len, void *data)
+{
+	struct setup_rw_req *setup = data;
+	int n, ref;
+	struct grant *gnt_list_entry;
+	unsigned int fsect, lsect;
+	/* Convenient aliases */
+	unsigned int grant_idx = setup->grant_idx;
+	struct blkif_request *ring_req = setup->ring_req;
+	struct blkfront_info *info = setup->info;
+	struct blk_shadow *shadow = &info->shadow[setup->id];
+
+	if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
+	    (grant_idx % GRANTS_PER_INDIRECT_FRAME == 0)) {
+		if (setup->segments)
+			kunmap_atomic(setup->segments);
+
+		n = grant_idx / GRANTS_PER_INDIRECT_FRAME;
+		gnt_list_entry = get_indirect_grant(&setup->gref_head, info);
+		shadow->indirect_grants[n] = gnt_list_entry;
+		setup->segments = kmap_atomic(gnt_list_entry->page);
+		ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
+	}
+
+	gnt_list_entry = get_grant(&setup->gref_head, gfn, info);
+	ref = gnt_list_entry->gref;
+	shadow->grants_used[grant_idx] = gnt_list_entry;
+
+	if (setup->need_copy) {
+		void *shared_data;
+
+		shared_data = kmap_atomic(gnt_list_entry->page);
+		/*
+		 * this does not wipe data stored outside the
+		 * range sg->offset..sg->offset+sg->length.
+		 * Therefore, blkback *could* see data from
+		 * previous requests. This is OK as long as
+		 * persistent grants are shared with just one
+		 * domain. It may need refactoring if this
+		 * changes
+		 */
+		memcpy(shared_data + offset,
+		       setup->bvec_data + setup->bvec_off,
+		       len);
+
+		kunmap_atomic(shared_data);
+		setup->bvec_off += len;
+	}
+
+	fsect = offset >> 9;
+	lsect = fsect + (len >> 9) - 1;
+	if (ring_req->operation != BLKIF_OP_INDIRECT) {
+		ring_req->u.rw.seg[grant_idx] =
+			(struct blkif_request_segment) {
+				.gref       = ref,
+				.first_sect = fsect,
+				.last_sect  = lsect };
+	} else {
+		setup->segments[grant_idx % GRANTS_PER_INDIRECT_FRAME] =
+			(struct blkif_request_segment) {
+				.gref       = ref,
+				.first_sect = fsect,
+				.last_sect  = lsect };
+	}
+
+	(setup->grant_idx)++;
+}
+
 static int blkif_queue_rw_req(struct request *req)
 {
 	struct blkfront_info *info = req->rq_disk->private_data;
 	struct blkif_request *ring_req;
 	unsigned long id;
-	unsigned int fsect, lsect;
-	int i, ref, n;
-	struct blkif_request_segment *segments = NULL;
+	int i;
+	struct setup_rw_req setup = {
+		.grant_idx = 0,
+		.segments = NULL,
+		.info = info,
+		.need_copy = rq_data_dir(req) && info->feature_persistent,
+	};
 
 	/*
 	 * Used to store if we are able to queue the request by just using
@@ -481,25 +586,23 @@ static int blkif_queue_rw_req(struct request *req)
 	 * as there are not sufficiently many free.
 	 */
 	bool new_persistent_gnts;
-	grant_ref_t gref_head;
-	struct grant *gnt_list_entry = NULL;
 	struct scatterlist *sg;
-	int nseg, max_grefs;
+	int num_sg, max_grefs, num_grant;
 
-	max_grefs = req->nr_phys_segments;
+	max_grefs = req->nr_phys_segments * GRANTS_PER_PSEG;
 	if (max_grefs > BLKIF_MAX_SEGMENTS_PER_REQUEST)
 		/*
 		 * If we are using indirect segments we need to account
 		 * for the indirect grefs used in the request.
 		 */
-		max_grefs += INDIRECT_GREFS(req->nr_phys_segments);
+		max_grefs += INDIRECT_GREFS(max_grefs);
 
 	/* Check if we have enough grants to allocate a requests */
 	if (info->persistent_gnts_c < max_grefs) {
 		new_persistent_gnts = 1;
 		if (gnttab_alloc_grant_references(
 		    max_grefs - info->persistent_gnts_c,
-		    &gref_head) < 0) {
+		    &setup.gref_head) < 0) {
 			gnttab_request_free_callback(
 				&info->callback,
 				blkif_restart_queue_callback,
@@ -516,12 +619,19 @@ static int blkif_queue_rw_req(struct request *req)
 	info->shadow[id].request = req;
 
 	BUG_ON(info->max_indirect_segments == 0 &&
-	       req->nr_phys_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
+	       GREFS(req->nr_phys_segments) > BLKIF_MAX_SEGMENTS_PER_REQUEST);
 	BUG_ON(info->max_indirect_segments &&
-	       req->nr_phys_segments > info->max_indirect_segments);
-	nseg = blk_rq_map_sg(req->q, req, info->shadow[id].sg);
+	       GREFS(req->nr_phys_segments) > info->max_indirect_segments);
+
+	num_sg = blk_rq_map_sg(req->q, req, info->shadow[id].sg);
+	num_grant = 0;
+	/* Calculate the number of grant used */
+	for_each_sg(info->shadow[id].sg, sg, num_sg, i)
+	       num_grant += gnttab_count_grant(sg->offset, sg->length);
+
 	ring_req->u.rw.id = id;
-	if (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST) {
+	info->shadow[id].num_sg = num_sg;
+	if (num_grant > BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 		/*
 		 * The indirect operation can only be a BLKIF_OP_READ or
 		 * BLKIF_OP_WRITE
@@ -532,7 +642,7 @@ static int blkif_queue_rw_req(struct request *req)
 			BLKIF_OP_WRITE : BLKIF_OP_READ;
 		ring_req->u.indirect.sector_number = (blkif_sector_t)blk_rq_pos(req);
 		ring_req->u.indirect.handle = info->handle;
-		ring_req->u.indirect.nr_segments = nseg;
+		ring_req->u.indirect.nr_segments = num_grant;
 	} else {
 		ring_req->u.rw.sector_number = (blkif_sector_t)blk_rq_pos(req);
 		ring_req->u.rw.handle = info->handle;
@@ -560,73 +670,30 @@ static int blkif_queue_rw_req(struct request *req)
 				ring_req->operation = 0;
 			}
 		}
-		ring_req->u.rw.nr_segments = nseg;
-	}
-	for_each_sg(info->shadow[id].sg, sg, nseg, i) {
-		fsect = sg->offset >> 9;
-		lsect = fsect + (sg->length >> 9) - 1;
-
-		if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
-		    (i % SEGS_PER_INDIRECT_FRAME == 0)) {
-			if (segments)
-				kunmap_atomic(segments);
-
-			n = i / SEGS_PER_INDIRECT_FRAME;
-			gnt_list_entry = get_indirect_grant(&gref_head, info);
-			info->shadow[id].indirect_grants[n] = gnt_list_entry;
-			segments = kmap_atomic(gnt_list_entry->page);
-			ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
-		}
-
-		gnt_list_entry = get_grant(&gref_head,
-					   xen_page_to_gfn(sg_page(sg)),
-					   info);
-		ref = gnt_list_entry->gref;
-
-		info->shadow[id].grants_used[i] = gnt_list_entry;
-
-		if (rq_data_dir(req) && info->feature_persistent) {
-			char *bvec_data;
-			void *shared_data;
+		ring_req->u.rw.nr_segments = num_grant;
+	}
 
-			BUG_ON(sg->offset + sg->length > PAGE_SIZE);
+	setup.ring_req = ring_req;
+	setup.id = id;
+	for_each_sg(info->shadow[id].sg, sg, num_sg, i) {
+		BUG_ON(sg->offset + sg->length > PAGE_SIZE);
 
-			shared_data = kmap_atomic(gnt_list_entry->page);
-			bvec_data = kmap_atomic(sg_page(sg));
+		if (setup.need_copy) {
+			setup.bvec_off = sg->offset;
+			setup.bvec_data = kmap_atomic(sg_page(sg));
+		}
 
-			/*
-			 * this does not wipe data stored outside the
-			 * range sg->offset..sg->offset+sg->length.
-			 * Therefore, blkback *could* see data from
-			 * previous requests. This is OK as long as
-			 * persistent grants are shared with just one
-			 * domain. It may need refactoring if this
-			 * changes
-			 */
-			memcpy(shared_data + sg->offset,
-			       bvec_data   + sg->offset,
-			       sg->length);
+		gnttab_foreach_grant_in_range(sg_page(sg),
+					      sg->offset,
+					      sg->length,
+					      blkif_setup_rw_req_grant,
+					      &setup);
 
-			kunmap_atomic(bvec_data);
-			kunmap_atomic(shared_data);
-		}
-		if (ring_req->operation != BLKIF_OP_INDIRECT) {
-			ring_req->u.rw.seg[i] =
-					(struct blkif_request_segment) {
-						.gref       = ref,
-						.first_sect = fsect,
-						.last_sect  = lsect };
-		} else {
-			n = i % SEGS_PER_INDIRECT_FRAME;
-			segments[n] =
-				(struct blkif_request_segment) {
-						.gref       = ref,
-						.first_sect = fsect,
-						.last_sect  = lsect };
-		}
+		if (setup.need_copy)
+			kunmap_atomic(setup.bvec_data);
 	}
-	if (segments)
-		kunmap_atomic(segments);
+	if (setup.segments)
+		kunmap_atomic(setup.segments);
 
 	info->ring.req_prod_pvt++;
 
@@ -634,7 +701,7 @@ static int blkif_queue_rw_req(struct request *req)
 	info->shadow[id].req = *ring_req;
 
 	if (new_persistent_gnts)
-		gnttab_free_grant_references(gref_head);
+		gnttab_free_grant_references(setup.gref_head);
 
 	return 0;
 }
@@ -751,14 +818,14 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
 	blk_queue_logical_block_size(rq, sector_size);
 	blk_queue_physical_block_size(rq, physical_sector_size);
-	blk_queue_max_hw_sectors(rq, (segments * PAGE_SIZE) / 512);
+	blk_queue_max_hw_sectors(rq, (segments * XEN_PAGE_SIZE) / 512);
 
 	/* Each segment in a request is up to an aligned page in size. */
 	blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
 	blk_queue_max_segment_size(rq, PAGE_SIZE);
 
 	/* Ensure a merged request will fit in a single I/O ring slot. */
-	blk_queue_max_segments(rq, segments);
+	blk_queue_max_segments(rq, segments / GRANTS_PER_PSEG);
 
 	/* Make sure buffer addresses are sector-aligned. */
 	blk_queue_dma_alignment(rq, 511);
@@ -1117,32 +1184,65 @@ free_shadow:
 
 }
 
+struct copy_from_grant {
+	const struct blk_shadow *s;
+	unsigned int grant_idx;
+	unsigned int bvec_offset;
+	char *bvec_data;
+};
+
+static void blkif_copy_from_grant(unsigned long gfn, unsigned int offset,
+				  unsigned int len, void *data)
+{
+	struct copy_from_grant *info = data;
+	char *shared_data;
+	/* Convenient aliases */
+	const struct blk_shadow *s = info->s;
+
+	shared_data = kmap_atomic(s->grants_used[info->grant_idx]->page);
+
+	memcpy(info->bvec_data + info->bvec_offset,
+	       shared_data + offset, len);
+
+	info->bvec_offset += len;
+	info->grant_idx++;
+
+	kunmap_atomic(shared_data);
+}
+
 static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
 			     struct blkif_response *bret)
 {
 	int i = 0;
 	struct scatterlist *sg;
-	char *bvec_data;
-	void *shared_data;
-	int nseg;
+	int num_sg, num_grant;
+	struct copy_from_grant data = {
+		.s = s,
+		.grant_idx = 0,
+	};
 
-	nseg = s->req.operation == BLKIF_OP_INDIRECT ?
+	num_grant = s->req.operation == BLKIF_OP_INDIRECT ?
 		s->req.u.indirect.nr_segments : s->req.u.rw.nr_segments;
+	num_sg = s->num_sg;
 
 	if (bret->operation == BLKIF_OP_READ && info->feature_persistent) {
-		for_each_sg(s->sg, sg, nseg, i) {
+		for_each_sg(s->sg, sg, num_sg, i) {
 			BUG_ON(sg->offset + sg->length > PAGE_SIZE);
-			shared_data = kmap_atomic(s->grants_used[i]->page);
-			bvec_data = kmap_atomic(sg_page(sg));
-			memcpy(bvec_data   + sg->offset,
-			       shared_data + sg->offset,
-			       sg->length);
-			kunmap_atomic(bvec_data);
-			kunmap_atomic(shared_data);
+
+			data.bvec_offset = sg->offset;
+			data.bvec_data = kmap_atomic(sg_page(sg));
+
+			gnttab_foreach_grant_in_range(sg_page(sg),
+						      sg->offset,
+						      sg->length,
+						      blkif_copy_from_grant,
+						      &data);
+
+			kunmap_atomic(data.bvec_data);
 		}
 	}
 	/* Add the persistent grant into the list of free grants */
-	for (i = 0; i < nseg; i++) {
+	for (i = 0; i < num_grant; i++) {
 		if (gnttab_query_foreign_access(s->grants_used[i]->gref)) {
 			/*
 			 * If the grant is still mapped by the backend (the
@@ -1168,7 +1268,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
 		}
 	}
 	if (s->req.operation == BLKIF_OP_INDIRECT) {
-		for (i = 0; i < INDIRECT_GREFS(nseg); i++) {
+		for (i = 0; i < INDIRECT_GREFS(num_grant); i++) {
 			if (gnttab_query_foreign_access(s->indirect_grants[i]->gref)) {
 				if (!info->feature_persistent)
 					pr_alert_ratelimited("backed has not unmapped grant: %u\n",
@@ -1312,7 +1412,7 @@ static int setup_blkring(struct xenbus_device *dev,
 {
 	struct blkif_sring *sring;
 	int err, i;
-	unsigned long ring_size = info->nr_ring_pages * PAGE_SIZE;
+	unsigned long ring_size = info->nr_ring_pages * XEN_PAGE_SIZE;
 	grant_ref_t gref[XENBUS_MAX_RING_PAGES];
 
 	for (i = 0; i < info->nr_ring_pages; i++)
@@ -1643,8 +1743,8 @@ static int blkif_recover(struct blkfront_info *info)
 			atomic_set(&split_bio->pending, pending);
 			split_bio->bio = bio;
 			for (i = 0; i < pending; i++) {
-				offset = (i * segs * PAGE_SIZE) >> 9;
-				size = min((unsigned int)(segs * PAGE_SIZE) >> 9,
+				offset = (i * segs * XEN_PAGE_SIZE) >> 9;
+				size = min((unsigned int)(segs * XEN_PAGE_SIZE) >> 9,
 					   (unsigned int)bio_sectors(bio) - offset);
 				cloned_bio = bio_clone(bio, GFP_NOIO);
 				BUG_ON(cloned_bio == NULL);
@@ -1755,15 +1855,17 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 
 static int blkfront_setup_indirect(struct blkfront_info *info)
 {
-	unsigned int segs;
+	unsigned int psegs, grants;
 	int err, i;
 
 	if (info->max_indirect_segments == 0)
-		segs = BLKIF_MAX_SEGMENTS_PER_REQUEST;
+		grants = BLKIF_MAX_SEGMENTS_PER_REQUEST;
 	else
-		segs = info->max_indirect_segments;
+		grants = info->max_indirect_segments;
+	psegs = grants / GRANTS_PER_PSEG;
 
-	err = fill_grant_buffer(info, (segs + INDIRECT_GREFS(segs)) * BLK_RING_SIZE(info));
+	err = fill_grant_buffer(info,
+				(grants + INDIRECT_GREFS(grants)) * BLK_RING_SIZE(info));
 	if (err)
 		goto out_of_memory;
 
@@ -1773,7 +1875,7 @@ static int blkfront_setup_indirect(struct blkfront_info *info)
 		 * grants, we need to allocate a set of pages that can be
 		 * used for mapping indirect grefs
 		 */
-		int num = INDIRECT_GREFS(segs) * BLK_RING_SIZE(info);
+		int num = INDIRECT_GREFS(grants) * BLK_RING_SIZE(info);
 
 		BUG_ON(!list_empty(&info->indirect_pages));
 		for (i = 0; i < num; i++) {
@@ -1786,20 +1888,20 @@ static int blkfront_setup_indirect(struct blkfront_info *info)
 
 	for (i = 0; i < BLK_RING_SIZE(info); i++) {
 		info->shadow[i].grants_used = kzalloc(
-			sizeof(info->shadow[i].grants_used[0]) * segs,
+			sizeof(info->shadow[i].grants_used[0]) * grants,
 			GFP_NOIO);
-		info->shadow[i].sg = kzalloc(sizeof(info->shadow[i].sg[0]) * segs, GFP_NOIO);
+		info->shadow[i].sg = kzalloc(sizeof(info->shadow[i].sg[0]) * psegs, GFP_NOIO);
 		if (info->max_indirect_segments)
 			info->shadow[i].indirect_grants = kzalloc(
 				sizeof(info->shadow[i].indirect_grants[0]) *
-				INDIRECT_GREFS(segs),
+				INDIRECT_GREFS(grants),
 				GFP_NOIO);
 		if ((info->shadow[i].grants_used == NULL) ||
 			(info->shadow[i].sg == NULL) ||
 		     (info->max_indirect_segments &&
 		     (info->shadow[i].indirect_grants == NULL)))
 			goto out_of_memory;
-		sg_init_table(info->shadow[i].sg, segs);
+		sg_init_table(info->shadow[i].sg, psegs);
 	}
 
 
-- 
2.1.4

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#1220289 — [PATCH v4 20/20] arm/xen: Add support for 64KB page granularity

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:50 +0200
Subject	[PATCH v4 20/20] arm/xen: Add support for 64KB page granularity
Message-ID	<q66Qa-1px-27@gated-at.bofh.it>
In reply to	#1220282

The hypercall interface is always using 4KB page granularity. This is
requiring to use xen page definition macro when we deal with hypercall.

Note that pfn_to_gfn is working with a Xen pfn (i.e 4KB). We may want to
rename pfn_gfn to make this explicit.

We also allocate a 64KB page for the shared page even though only the
first 4KB is used. I don't think this is really important for now as it
helps to have the pointer 4KB aligned (XENMEM_add_to_physmap is taking a
Xen PFN).

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---
Cc: Russell King <linux@arm.linux.org.uk>

Stefano, I've dropped your reviewed-by given I've updated the doc and do
changes to avoid usage of XEN_PAGE_SHIFT

    Changes in v4:
        - Add Stefano's Reviewed-by

    Changes in v3:
        - s/MFN/GFN/ base on the new naming
        - Use virt_to_gfn to avoid use XEN_PAGE_SHIFT
        - Drop Stefano's reviewed-by
        - Add some docs in arch/arm/asm/xen/page.h

    Changes in v2
        - Add Stefano's reviewed-by
---
 arch/arm/include/asm/xen/page.h | 15 +++++++++++++--
 arch/arm/xen/enlighten.c        |  6 +++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index 98c9fc3..e3d94cf 100644
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -28,6 +28,17 @@ typedef struct xpaddr {
 
 #define INVALID_P2M_ENTRY      (~0UL)
 
+/*
+ * The pseudo-physical frame (pfn) used in all the helpers is always based
+ * on Xen page granularity (i.e 4KB).
+ *
+ * A Linux page may be split across multiple non-contiguous Xen page so we
+ * have to keep track with frame based on 4KB page granularity.
+ *
+ * PV drivers should never make a direct usage of those helpers (particularly
+ * pfn_to_gfn and gfn_to_pfn).
+ */
+
 unsigned long __pfn_to_mfn(unsigned long pfn);
 extern struct rb_root phys_to_mach;
 
@@ -64,8 +75,8 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn)
 #define bfn_to_local_pfn(bfn)	bfn_to_pfn(bfn)
 
 /* VIRT <-> GUEST conversion */
-#define virt_to_gfn(v)		(pfn_to_gfn(virt_to_pfn(v)))
-#define gfn_to_virt(m)		(__va(gfn_to_pfn(m) << PAGE_SHIFT))
+#define virt_to_gfn(v)		(pfn_to_gfn(virt_to_phys(v) >> XEN_PAGE_SHIFT))
+#define gfn_to_virt(m)		(__va(gfn_to_pfn(m) << XEN_PAGE_SHIFT))
 
 /* Only used in PV code. But ARM guests are always HVM. */
 static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index eeeab07..50b4769 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -89,8 +89,8 @@ static void xen_percpu_init(void)
 	pr_info("Xen: initializing cpu%d\n", cpu);
 	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
 
-	info.mfn = __pa(vcpup) >> PAGE_SHIFT;
-	info.offset = offset_in_page(vcpup);
+	info.mfn = virt_to_gfn(vcpup);
+	info.offset = xen_offset_in_page(vcpup);
 
 	err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, cpu, &info);
 	BUG_ON(err);
@@ -213,7 +213,7 @@ static int __init xen_guest_init(void)
 	xatp.domid = DOMID_SELF;
 	xatp.idx = 0;
 	xatp.space = XENMAPSPACE_shared_info;
-	xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
+	xatp.gpfn = virt_to_gfn(shared_info_page);
 	if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
 		BUG();
 
-- 
2.1.4

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#1220291 — [PATCH v4 17/20] net/xen-netfront: Make it running on 64KB page granularity

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:50 +0200
Subject	[PATCH v4 17/20] net/xen-netfront: Make it running on 64KB page granularity
Message-ID	<q66Qa-1px-29@gated-at.bofh.it>
In reply to	#1220282

The PV network protocol is using 4KB page granularity. The goal of this
patch is to allow a Linux using 64KB page granularity using network
device on a non-modified Xen.

It's only necessary to adapt the ring size and break skb data in small
chunk of 4KB. The rest of the code is relying on the grant table code.

Note that we allocate a Linux page for each rx skb but only the first
4KB is used. We may improve the memory usage by extending the size of
the rx skb.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>

---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: netdev@vger.kernel.org

Improvement such as support of 64KB grant is not taken into
consideration in this patch because we have the requirement to run a Linux
using 64KB pages on a non-modified Xen.

Tested with workload such as ping, ssh, wget, git... I would happy if
someone give details how to test all the path.

    Changes in v4:
        - s/gnttab_one_grant/gnttab_for_one_grant/ based on the new naming
        - Add David's reviewed-by

    Changes in v3:
        - Fix errors reported by checkpatch.pl
        - s/mfn/gfn/ base on the new naming
        - xennet_tx_setup_grant was calling itself resulting an
        guest stall when using iperf.
        - The grant callback doesn't allow anymore to change the len
        (wasn't used here)
        - gnttab_foreach_grant has been renamed to gnttab_foreach_grant_in_range
        - gnttab_page_grant_foreign_ref has been renamed to
        gnttab_foreach_grant_foreign_ref_one

    Changes in v2:
        - Use gnttab_foreach_grant to split a Linux page in grant
        - Fix count slots
---
 drivers/net/xen-netfront.c | 122 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 86 insertions(+), 36 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 47f791e..17b1013 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -74,8 +74,8 @@ struct netfront_cb {
 
 #define GRANT_INVALID_REF	0
 
-#define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
-#define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)
+#define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, XEN_PAGE_SIZE)
+#define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, XEN_PAGE_SIZE)
 
 /* Minimum number of Rx slots (includes slot for GSO metadata). */
 #define NET_RX_SLOTS_MIN (XEN_NETIF_NR_SLOTS_MIN + 1)
@@ -291,7 +291,7 @@ static void xennet_alloc_rx_buffers(struct netfront_queue *queue)
 		struct sk_buff *skb;
 		unsigned short id;
 		grant_ref_t ref;
-		unsigned long gfn;
+		struct page *page;
 		struct xen_netif_rx_request *req;
 
 		skb = xennet_alloc_one_rx_buffer(queue);
@@ -307,14 +307,13 @@ static void xennet_alloc_rx_buffers(struct netfront_queue *queue)
 		BUG_ON((signed short)ref < 0);
 		queue->grant_rx_ref[id] = ref;
 
-		gfn = xen_page_to_gfn(skb_frag_page(&skb_shinfo(skb)->frags[0]));
+		page = skb_frag_page(&skb_shinfo(skb)->frags[0]);
 
 		req = RING_GET_REQUEST(&queue->rx, req_prod);
-		gnttab_grant_foreign_access_ref(ref,
-						queue->info->xbdev->otherend_id,
-						gfn,
-						0);
-
+		gnttab_page_grant_foreign_access_ref_one(ref,
+							 queue->info->xbdev->otherend_id,
+							 page,
+							 0);
 		req->id = id;
 		req->gref = ref;
 	}
@@ -415,25 +414,33 @@ static void xennet_tx_buf_gc(struct netfront_queue *queue)
 	xennet_maybe_wake_tx(queue);
 }
 
-static struct xen_netif_tx_request *xennet_make_one_txreq(
-	struct netfront_queue *queue, struct sk_buff *skb,
-	struct page *page, unsigned int offset, unsigned int len)
+struct xennet_gnttab_make_txreq {
+	struct netfront_queue *queue;
+	struct sk_buff *skb;
+	struct page *page;
+	struct xen_netif_tx_request *tx; /* Last request */
+	unsigned int size;
+};
+
+static void xennet_tx_setup_grant(unsigned long gfn, unsigned int offset,
+				  unsigned int len, void *data)
 {
+	struct xennet_gnttab_make_txreq *info = data;
 	unsigned int id;
 	struct xen_netif_tx_request *tx;
 	grant_ref_t ref;
-
-	len = min_t(unsigned int, PAGE_SIZE - offset, len);
+	/* convenient aliases */
+	struct page *page = info->page;
+	struct netfront_queue *queue = info->queue;
+	struct sk_buff *skb = info->skb;
 
 	id = get_id_from_freelist(&queue->tx_skb_freelist, queue->tx_skbs);
 	tx = RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);
 	ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
 	BUG_ON((signed short)ref < 0);
 
-	gnttab_grant_foreign_access_ref(ref,
-					queue->info->xbdev->otherend_id,
-					xen_page_to_gfn(page),
-					GNTMAP_readonly);
+	gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,
+					gfn, GNTMAP_readonly);
 
 	queue->tx_skbs[id].skb = skb;
 	queue->grant_tx_page[id] = page;
@@ -445,7 +452,34 @@ static struct xen_netif_tx_request *xennet_make_one_txreq(
 	tx->size = len;
 	tx->flags = 0;
 
-	return tx;
+	info->tx = tx;
+	info->size += tx->size;
+}
+
+static struct xen_netif_tx_request *xennet_make_first_txreq(
+	struct netfront_queue *queue, struct sk_buff *skb,
+	struct page *page, unsigned int offset, unsigned int len)
+{
+	struct xennet_gnttab_make_txreq info = {
+		.queue = queue,
+		.skb = skb,
+		.page = page,
+		.size = 0,
+	};
+
+	gnttab_for_one_grant(page, offset, len, xennet_tx_setup_grant, &info);
+
+	return info.tx;
+}
+
+static void xennet_make_one_txreq(unsigned long gfn, unsigned int offset,
+				  unsigned int len, void *data)
+{
+	struct xennet_gnttab_make_txreq *info = data;
+
+	info->tx->flags |= XEN_NETTXF_more_data;
+	skb_get(info->skb);
+	xennet_tx_setup_grant(gfn, offset, len, data);
 }
 
 static struct xen_netif_tx_request *xennet_make_txreqs(
@@ -453,20 +487,30 @@ static struct xen_netif_tx_request *xennet_make_txreqs(
 	struct sk_buff *skb, struct page *page,
 	unsigned int offset, unsigned int len)
 {
+	struct xennet_gnttab_make_txreq info = {
+		.queue = queue,
+		.skb = skb,
+		.tx = tx,
+	};
+
 	/* Skip unused frames from start of page */
 	page += offset >> PAGE_SHIFT;
 	offset &= ~PAGE_MASK;
 
 	while (len) {
-		tx->flags |= XEN_NETTXF_more_data;
-		tx = xennet_make_one_txreq(queue, skb_get(skb),
-					   page, offset, len);
+		info.page = page;
+		info.size = 0;
+
+		gnttab_foreach_grant_in_range(page, offset, len,
+					      xennet_make_one_txreq,
+					      &info);
+
 		page++;
 		offset = 0;
-		len -= tx->size;
+		len -= info.size;
 	}
 
-	return tx;
+	return info.tx;
 }
 
 /*
@@ -476,9 +520,10 @@ static struct xen_netif_tx_request *xennet_make_txreqs(
 static int xennet_count_skb_slots(struct sk_buff *skb)
 {
 	int i, frags = skb_shinfo(skb)->nr_frags;
-	int pages;
+	int slots;
 
-	pages = PFN_UP(offset_in_page(skb->data) + skb_headlen(skb));
+	slots = gnttab_count_grant(offset_in_page(skb->data),
+				   skb_headlen(skb));
 
 	for (i = 0; i < frags; i++) {
 		skb_frag_t *frag = skb_shinfo(skb)->frags + i;
@@ -488,10 +533,10 @@ static int xennet_count_skb_slots(struct sk_buff *skb)
 		/* Skip unused frames from start of page */
 		offset &= ~PAGE_MASK;
 
-		pages += PFN_UP(offset + size);
+		slots += gnttab_count_grant(offset, size);
 	}
 
-	return pages;
+	return slots;
 }
 
 static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb,
@@ -512,6 +557,8 @@ static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb,
 	return queue_idx;
 }
 
+#define MAX_XEN_SKB_FRAGS (65536 / XEN_PAGE_SIZE + 1)
+
 static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct netfront_info *np = netdev_priv(dev);
@@ -546,7 +593,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	slots = xennet_count_skb_slots(skb);
-	if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
+	if (unlikely(slots > MAX_XEN_SKB_FRAGS + 1)) {
 		net_dbg_ratelimited("xennet: skb rides the rocket: %d slots, %d bytes\n",
 				    slots, skb->len);
 		if (skb_linearize(skb))
@@ -567,10 +614,13 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	/* First request for the linear area. */
-	first_tx = tx = xennet_make_one_txreq(queue, skb,
-					      page, offset, len);
-	page++;
-	offset = 0;
+	first_tx = tx = xennet_make_first_txreq(queue, skb,
+						page, offset, len);
+	offset += tx->size;
+	if (offset == PAGE_SIZE) {
+		page++;
+		offset = 0;
+	}
 	len -= tx->size;
 
 	if (skb->ip_summed == CHECKSUM_PARTIAL)
@@ -732,7 +782,7 @@ static int xennet_get_responses(struct netfront_queue *queue,
 
 	for (;;) {
 		if (unlikely(rx->status < 0 ||
-			     rx->offset + rx->status > PAGE_SIZE)) {
+			     rx->offset + rx->status > XEN_PAGE_SIZE)) {
 			if (net_ratelimit())
 				dev_warn(dev, "rx->offset: %u, size: %d\n",
 					 rx->offset, rx->status);
@@ -1495,7 +1545,7 @@ static int setup_netfront(struct xenbus_device *dev,
 		goto fail;
 	}
 	SHARED_RING_INIT(txs);
-	FRONT_RING_INIT(&queue->tx, txs, PAGE_SIZE);
+	FRONT_RING_INIT(&queue->tx, txs, XEN_PAGE_SIZE);
 
 	err = xenbus_grant_ring(dev, txs, 1, &gref);
 	if (err < 0)
@@ -1509,7 +1559,7 @@ static int setup_netfront(struct xenbus_device *dev,
 		goto alloc_rx_ring_fail;
 	}
 	SHARED_RING_INIT(rxs);
-	FRONT_RING_INIT(&queue->rx, rxs, PAGE_SIZE);
+	FRONT_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE);
 
 	err = xenbus_grant_ring(dev, rxs, 1, &gref);
 	if (err < 0)
-- 
2.1.4

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#1220293 — [PATCH v4 10/20] xen/xenbus: Use Xen page definition

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:50 +0200
Subject	[PATCH v4 10/20] xen/xenbus: Use Xen page definition
Message-ID	<q66Qa-1px-31@gated-at.bofh.it>
In reply to	#1220282

All the ring (xenstore, and PV rings) are always based on the page
granularity of Xen.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>

    Changes in v3:
        - Fix errors reported by checkpatch.pl
        - s/MFN/GFN base on the new naming
        - Add David and Stefano's reviewed-by

    Changes in v2:
        - Also update the ring mapping function
---
 drivers/xen/xenbus/xenbus_client.c | 6 +++---
 drivers/xen/xenbus/xenbus_probe.c  | 3 ++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 2ba09c1..359e654 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -388,7 +388,7 @@ int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
 		}
 		grefs[i] = err;
 
-		vaddr = vaddr + PAGE_SIZE;
+		vaddr = vaddr + XEN_PAGE_SIZE;
 	}
 
 	return 0;
@@ -555,7 +555,7 @@ static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
 	if (!node)
 		return -ENOMEM;
 
-	area = alloc_vm_area(PAGE_SIZE * nr_grefs, ptes);
+	area = alloc_vm_area(XEN_PAGE_SIZE * nr_grefs, ptes);
 	if (!area) {
 		kfree(node);
 		return -ENOMEM;
@@ -750,7 +750,7 @@ static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
 		unsigned long addr;
 
 		memset(&unmap[i], 0, sizeof(unmap[i]));
-		addr = (unsigned long)vaddr + (PAGE_SIZE * i);
+		addr = (unsigned long)vaddr + (XEN_PAGE_SIZE * i);
 		unmap[i].host_addr = arbitrary_virt_to_machine(
 			lookup_address(addr, &level)).maddr;
 		unmap[i].dev_bus_addr = 0;
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 3cbe055..33a31cf 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -802,7 +802,8 @@ static int __init xenbus_init(void)
 			goto out_error;
 		xen_store_gfn = (unsigned long)v;
 		xen_store_interface =
-			xen_remap(xen_store_gfn << PAGE_SHIFT, PAGE_SIZE);
+			xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
+				  XEN_PAGE_SIZE);
 		break;
 	default:
 		pr_warn("Xenstore state unknown\n");
-- 
2.1.4

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#1220295 — [PATCH v4 16/20] block/xen-blkback: Make it running on 64KB page granularity

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:50 +0200
Subject	[PATCH v4 16/20] block/xen-blkback: Make it running on 64KB page granularity
Message-ID	<q66Qa-1px-35@gated-at.bofh.it>
In reply to	#1220282

The PV block protocol is using 4KB page granularity. The goal of this
patch is to allow a Linux using 64KB page granularity behaving as a
block backend on a non-modified Xen.

It's only necessary to adapt the ring size and the number of request per
indirect frames. The rest of the code is relying on the grant table
code.

Note that the grant table code is allocating a Linux page per grant
which will result to waste 6OKB for every grant when Linux is using 64KB
page granularity. This could be improved by sharing the page between
multiple grants.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Acked-by: "Roger Pau Monné" <roger.pau@citrix.com>
---

Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>

Improvement such as support of 64KB grant is not taken into
consideration in this patch because we have the requirement to run a
Linux using 64KB pages on a non-modified Xen.

This has been tested only with a loop device. I plan to test passing
hard drive partition but I didn't yet convert the swiotlb code.

    Changes in v4:
        - Add Roger's acked-by

    Changes in v3:
        - Use DIV_ROUND_UP in INDIRECT_PAGES to avoid a line over 80
        characters
---
 drivers/block/xen-blkback/blkback.c |  5 +++--
 drivers/block/xen-blkback/common.h  | 17 +++++++++++++----
 drivers/block/xen-blkback/xenbus.c  |  9 ++++++---
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 954c002..802319a 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -961,7 +961,7 @@ static int xen_blkbk_parse_indirect(struct blkif_request *req,
 		seg[n].nsec = segments[i].last_sect -
 			segments[i].first_sect + 1;
 		seg[n].offset = (segments[i].first_sect << 9);
-		if ((segments[i].last_sect >= (PAGE_SIZE >> 9)) ||
+		if ((segments[i].last_sect >= (XEN_PAGE_SIZE >> 9)) ||
 		    (segments[i].last_sect < segments[i].first_sect)) {
 			rc = -EINVAL;
 			goto unmap;
@@ -1210,6 +1210,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 
 	req_operation = req->operation == BLKIF_OP_INDIRECT ?
 			req->u.indirect.indirect_op : req->operation;
+
 	if ((req->operation == BLKIF_OP_INDIRECT) &&
 	    (req_operation != BLKIF_OP_READ) &&
 	    (req_operation != BLKIF_OP_WRITE)) {
@@ -1268,7 +1269,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 			seg[i].nsec = req->u.rw.seg[i].last_sect -
 				req->u.rw.seg[i].first_sect + 1;
 			seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
-			if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
+			if ((req->u.rw.seg[i].last_sect >= (XEN_PAGE_SIZE >> 9)) ||
 			    (req->u.rw.seg[i].last_sect <
 			     req->u.rw.seg[i].first_sect))
 				goto fail_response;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 45a044a..68e87a0 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -39,6 +39,7 @@
 #include <asm/pgalloc.h>
 #include <asm/hypervisor.h>
 #include <xen/grant_table.h>
+#include <xen/page.h>
 #include <xen/xenbus.h>
 #include <xen/interface/io/ring.h>
 #include <xen/interface/io/blkif.h>
@@ -51,12 +52,20 @@ extern unsigned int xen_blkif_max_ring_order;
  */
 #define MAX_INDIRECT_SEGMENTS 256
 
-#define SEGS_PER_INDIRECT_FRAME \
-	(PAGE_SIZE/sizeof(struct blkif_request_segment))
+/*
+ * Xen use 4K pages. The guest may use different page size (4K or 64K)
+ * Number of Xen pages per segment
+ */
+#define XEN_PAGES_PER_SEGMENT   (PAGE_SIZE / XEN_PAGE_SIZE)
+
+#define XEN_PAGES_PER_INDIRECT_FRAME \
+	(XEN_PAGE_SIZE/sizeof(struct blkif_request_segment))
+#define SEGS_PER_INDIRECT_FRAME	\
+	(XEN_PAGES_PER_INDIRECT_FRAME / XEN_PAGES_PER_SEGMENT)
+
 #define MAX_INDIRECT_PAGES \
 	((MAX_INDIRECT_SEGMENTS + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
-#define INDIRECT_PAGES(_segs) \
-	((_segs + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
+#define INDIRECT_PAGES(_segs) DIV_ROUND_UP(_segs, XEN_PAGES_PER_INDIRECT_FRAME)
 
 /* Not a real protocol.  Used to generate ring structs which contain
  * the elements common to all protocols only.  This way we get a
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index deb3f00..edd27e4 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -176,21 +176,24 @@ static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t *gref,
 	{
 		struct blkif_sring *sring;
 		sring = (struct blkif_sring *)blkif->blk_ring;
-		BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE * nr_grefs);
+		BACK_RING_INIT(&blkif->blk_rings.native, sring,
+			       XEN_PAGE_SIZE * nr_grefs);
 		break;
 	}
 	case BLKIF_PROTOCOL_X86_32:
 	{
 		struct blkif_x86_32_sring *sring_x86_32;
 		sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
-		BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE * nr_grefs);
+		BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32,
+			       XEN_PAGE_SIZE * nr_grefs);
 		break;
 	}
 	case BLKIF_PROTOCOL_X86_64:
 	{
 		struct blkif_x86_64_sring *sring_x86_64;
 		sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
-		BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE * nr_grefs);
+		BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64,
+			       XEN_PAGE_SIZE * nr_grefs);
 		break;
 	}
 	default:
-- 
2.1.4

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#1220298 — [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-07 17:50 +0200
Subject	[PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity
Message-ID	<q66Qa-1px-39@gated-at.bofh.it>
In reply to	#1220282

The PV network protocol is using 4KB page granularity. The goal of this
patch is to allow a Linux using 64KB page granularity working as a
network backend on a non-modified Xen.

It's only necessary to adapt the ring size and break skb data in small
chunk of 4KB. The rest of the code is relying on the grant table code.

Signed-off-by: Julien Grall <julien.grall@citrix.com>

---
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: netdev@vger.kernel.org

Improvement such as support of 64KB grant is not taken into
consideration in this patch because we have the requirement to run a
Linux using 64KB pages on a non-modified Xen.

Note that I haven't add a comment why the offset is 0 after the first
iteration. See [1] for more details.

[1] https://lkml.org/lkml/2015/8/10/456

    Changes in v4:
        - Add a comment to explain how we compute MAX_XEN_SKB_FRAGS

    Changes in v3:
        - Fix errors reported by checkpatch.pl
        - s/mfn/gfn/ based on the new naming
        - gnttab_foreach_grant has been renamed to gnttab_forach_grant_in_range
        - The grant callback doesn't allow anymore to use less data. An
        helpers has been added in netback to handle this.

    Changes in v2:
        - Correctly set MAX_GRANT_COPY_OPS and XEN_NETBK_RX_SLOTS_MAX
        - Don't use XEN_PAGE_SIZE in handle_frag_list as we coalesce
        fragment into a new skb
        - Use gnntab_foreach_grant to split a Linux page into grant
---
 drivers/net/xen-netback/common.h  |  18 +++--
 drivers/net/xen-netback/netback.c | 153 ++++++++++++++++++++++++--------------
 2 files changed, 110 insertions(+), 61 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 8a495b3..24cb365 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -44,6 +44,7 @@
 #include <xen/interface/grant_table.h>
 #include <xen/grant_table.h>
 #include <xen/xenbus.h>
+#include <xen/page.h>
 #include <linux/debugfs.h>
 
 typedef unsigned int pending_ring_idx_t;
@@ -64,8 +65,8 @@ struct pending_tx_info {
 	struct ubuf_info callback_struct;
 };
 
-#define XEN_NETIF_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
-#define XEN_NETIF_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)
+#define XEN_NETIF_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, XEN_PAGE_SIZE)
+#define XEN_NETIF_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, XEN_PAGE_SIZE)
 
 struct xenvif_rx_meta {
 	int id;
@@ -80,16 +81,21 @@ struct xenvif_rx_meta {
 /* Discriminate from any valid pending_idx value. */
 #define INVALID_PENDING_IDX 0xFFFF
 
-#define MAX_BUFFER_OFFSET PAGE_SIZE
+#define MAX_BUFFER_OFFSET XEN_PAGE_SIZE
 
 #define MAX_PENDING_REQS XEN_NETIF_TX_RING_SIZE
 
+/* The maximum number of frags is derived from the size of a grant (same
+ * as a Xen page size for now).
+ */
+#define MAX_XEN_SKB_FRAGS (65536 / XEN_PAGE_SIZE + 1)
+
 /* It's possible for an skb to have a maximal number of frags
  * but still be less than MAX_BUFFER_OFFSET in size. Thus the
- * worst-case number of copy operations is MAX_SKB_FRAGS per
+ * worst-case number of copy operations is MAX_XEN_SKB_FRAGS per
  * ring slot.
  */
-#define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)
+#define MAX_GRANT_COPY_OPS (MAX_XEN_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)
 
 #define NETBACK_INVALID_HANDLE -1
 
@@ -203,7 +209,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
 /* Maximum number of Rx slots a to-guest packet may use, including the
  * slot needed for GSO meta-data.
  */
-#define XEN_NETBK_RX_SLOTS_MAX (MAX_SKB_FRAGS + 1)
+#define XEN_NETBK_RX_SLOTS_MAX ((MAX_XEN_SKB_FRAGS + 1))
 
 enum state_bit_shift {
 	/* This bit marks that the vif is connected */
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index d4c1bc7..b1649aa 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -263,6 +263,80 @@ static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif_queue *queue,
 	return meta;
 }
 
+struct gop_frag_copy {
+	struct xenvif_queue *queue;
+	struct netrx_pending_operations *npo;
+	struct xenvif_rx_meta *meta;
+	int head;
+	int gso_type;
+
+	struct page *page;
+};
+
+static void xenvif_setup_copy_gop(unsigned long gfn,
+				  unsigned int offset,
+				  unsigned int *len,
+				  struct gop_frag_copy *info)
+{
+	struct gnttab_copy *copy_gop;
+	struct xen_page_foreign *foreign;
+	/* Convenient aliases */
+	struct xenvif_queue *queue = info->queue;
+	struct netrx_pending_operations *npo = info->npo;
+	struct page *page = info->page;
+
+	BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);
+
+	if (npo->copy_off == MAX_BUFFER_OFFSET)
+		info->meta = get_next_rx_buffer(queue, npo);
+
+	if (npo->copy_off + *len > MAX_BUFFER_OFFSET)
+		*len = MAX_BUFFER_OFFSET - npo->copy_off;
+
+	copy_gop = npo->copy + npo->copy_prod++;
+	copy_gop->flags = GNTCOPY_dest_gref;
+	copy_gop->len = *len;
+
+	foreign = xen_page_foreign(page);
+	if (foreign) {
+		copy_gop->source.domid = foreign->domid;
+		copy_gop->source.u.ref = foreign->gref;
+		copy_gop->flags |= GNTCOPY_source_gref;
+	} else {
+		copy_gop->source.domid = DOMID_SELF;
+		copy_gop->source.u.gmfn = gfn;
+	}
+	copy_gop->source.offset = offset;
+
+	copy_gop->dest.domid = queue->vif->domid;
+	copy_gop->dest.offset = npo->copy_off;
+	copy_gop->dest.u.ref = npo->copy_gref;
+
+	npo->copy_off += *len;
+	info->meta->size += *len;
+
+	/* Leave a gap for the GSO descriptor. */
+	if (info->head && ((1 << info->gso_type) & queue->vif->gso_mask))
+		queue->rx.req_cons++;
+
+	info->head = 0; /* There must be something in this buffer now */
+}
+
+static void xenvif_gop_frag_copy_grant(unsigned long gfn,
+				       unsigned offset,
+				       unsigned int len,
+				       void *data)
+{
+	unsigned int bytes;
+
+	while (len) {
+		bytes = len;
+		xenvif_setup_copy_gop(gfn, offset, &bytes, data);
+		offset += bytes;
+		len -= bytes;
+	}
+}
+
 /*
  * Set up the grant operations for this fragment. If it's a flipping
  * interface, we also set up the unmap request from here.
@@ -272,83 +346,52 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
 				 struct page *page, unsigned long size,
 				 unsigned long offset, int *head)
 {
-	struct gnttab_copy *copy_gop;
-	struct xenvif_rx_meta *meta;
+	struct gop_frag_copy info = {
+		.queue = queue,
+		.npo = npo,
+		.head = *head,
+		.gso_type = XEN_NETIF_GSO_TYPE_NONE,
+	};
 	unsigned long bytes;
-	int gso_type = XEN_NETIF_GSO_TYPE_NONE;
 
 	if (skb_is_gso(skb)) {
 		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
-			gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+			info.gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
 		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
-			gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
+			info.gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
 	}
 
 	/* Data must not cross a page boundary. */
 	BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));
 
-	meta = npo->meta + npo->meta_prod - 1;
+	info.meta = npo->meta + npo->meta_prod - 1;
 
 	/* Skip unused frames from start of page */
 	page += offset >> PAGE_SHIFT;
 	offset &= ~PAGE_MASK;
 
 	while (size > 0) {
-		struct xen_page_foreign *foreign;
-
 		BUG_ON(offset >= PAGE_SIZE);
-		BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);
-
-		if (npo->copy_off == MAX_BUFFER_OFFSET)
-			meta = get_next_rx_buffer(queue, npo);
 
 		bytes = PAGE_SIZE - offset;
 		if (bytes > size)
 			bytes = size;
 
-		if (npo->copy_off + bytes > MAX_BUFFER_OFFSET)
-			bytes = MAX_BUFFER_OFFSET - npo->copy_off;
-
-		copy_gop = npo->copy + npo->copy_prod++;
-		copy_gop->flags = GNTCOPY_dest_gref;
-		copy_gop->len = bytes;
-
-		foreign = xen_page_foreign(page);
-		if (foreign) {
-			copy_gop->source.domid = foreign->domid;
-			copy_gop->source.u.ref = foreign->gref;
-			copy_gop->flags |= GNTCOPY_source_gref;
-		} else {
-			copy_gop->source.domid = DOMID_SELF;
-			copy_gop->source.u.gmfn =
-				virt_to_gfn(page_address(page));
-		}
-		copy_gop->source.offset = offset;
-
-		copy_gop->dest.domid = queue->vif->domid;
-		copy_gop->dest.offset = npo->copy_off;
-		copy_gop->dest.u.ref = npo->copy_gref;
-
-		npo->copy_off += bytes;
-		meta->size += bytes;
-
-		offset += bytes;
+		info.page = page;
+		gnttab_foreach_grant_in_range(page, offset, bytes,
+					      xenvif_gop_frag_copy_grant,
+					      &info);
 		size -= bytes;
+		offset = 0;
 
-		/* Next frame */
-		if (offset == PAGE_SIZE && size) {
+		/* Next page */
+		if (size) {
 			BUG_ON(!PageCompound(page));
 			page++;
-			offset = 0;
 		}
-
-		/* Leave a gap for the GSO descriptor. */
-		if (*head && ((1 << gso_type) & queue->vif->gso_mask))
-			queue->rx.req_cons++;
-
-		*head = 0; /* There must be something in this buffer now. */
-
 	}
+
+	*head = info.head;
 }
 
 /*
@@ -747,7 +790,7 @@ static int xenvif_count_requests(struct xenvif_queue *queue,
 		first->size -= txp->size;
 		slots++;
 
-		if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) {
+		if (unlikely((txp->offset + txp->size) > XEN_PAGE_SIZE)) {
 			netdev_err(queue->vif->dev, "Cross page boundary, txp->offset: %u, size: %u\n",
 				 txp->offset, txp->size);
 			xenvif_fatal_tx_err(queue->vif);
@@ -1229,11 +1272,11 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue,
 		}
 
 		/* No crossing a page as the payload mustn't fragment. */
-		if (unlikely((txreq.offset + txreq.size) > PAGE_SIZE)) {
+		if (unlikely((txreq.offset + txreq.size) > XEN_PAGE_SIZE)) {
 			netdev_err(queue->vif->dev,
 				   "txreq.offset: %u, size: %u, end: %lu\n",
 				   txreq.offset, txreq.size,
-				   (unsigned long)(txreq.offset&~PAGE_MASK) + txreq.size);
+				   (unsigned long)(txreq.offset&~XEN_PAGE_MASK) + txreq.size);
 			xenvif_fatal_tx_err(queue->vif);
 			break;
 		}
@@ -1299,7 +1342,7 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue,
 			virt_to_gfn(skb->data);
 		queue->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
 		queue->tx_copy_ops[*copy_ops].dest.offset =
-			offset_in_page(skb->data);
+			offset_in_page(skb->data) & ~XEN_PAGE_MASK;
 
 		queue->tx_copy_ops[*copy_ops].len = data_len;
 		queue->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
@@ -1784,7 +1827,7 @@ int xenvif_map_frontend_rings(struct xenvif_queue *queue,
 		goto err;
 
 	txs = (struct xen_netif_tx_sring *)addr;
-	BACK_RING_INIT(&queue->tx, txs, PAGE_SIZE);
+	BACK_RING_INIT(&queue->tx, txs, XEN_PAGE_SIZE);
 
 	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
 				     &rx_ring_ref, 1, &addr);
@@ -1792,7 +1835,7 @@ int xenvif_map_frontend_rings(struct xenvif_queue *queue,
 		goto err;
 
 	rxs = (struct xen_netif_rx_sring *)addr;
-	BACK_RING_INIT(&queue->rx, rxs, PAGE_SIZE);
+	BACK_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE);
 
 	return 0;
 
-- 
2.1.4

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#1220335 — Re: [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

From	Wei Liu <wei.liu2@citrix.com>
Date	2015-09-07 19:00 +0200
Subject	Re: [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity
Message-ID	<q67VT-2VX-9@gated-at.bofh.it>
In reply to	#1220298

You might need to rebase you patch. A patch to netback went it recently.

On Mon, Sep 07, 2015 at 04:33:56PM +0100, Julien Grall wrote:
> The PV network protocol is using 4KB page granularity. The goal of this
> patch is to allow a Linux using 64KB page granularity working as a
> network backend on a non-modified Xen.
> 
> It's only necessary to adapt the ring size and break skb data in small
> chunk of 4KB. The rest of the code is relying on the grant table code.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> 

Reviewed-by: Wei Liu <wei.liu2@citrix.com>
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#1220697 — Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

From	Wei Liu <wei.liu2@citrix.com>
Date	2015-09-08 13:10 +0200
Subject	Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity
Message-ID	<q6oWJ-2qG-1@gated-at.bofh.it>
In reply to	#1220335

On Tue, Sep 08, 2015 at 12:07:31PM +0100, Julien Grall wrote:
> Hi Wei,
> 
> On 07/09/15 17:57, Wei Liu wrote:
> > You might need to rebase you patch. A patch to netback went it recently.
> 
> Do you mean 210c34dcd8d912dcc740f1f17625a7293af5cb56 "xen-netback: add
> support for multicast control"?
> 

Yes, that one.

> If so I didn't see any specific issue while rebasing on the latest
> linus' master.
> 

Good.

> > On Mon, Sep 07, 2015 at 04:33:56PM +0100, Julien Grall wrote:
> >> The PV network protocol is using 4KB page granularity. The goal of this
> >> patch is to allow a Linux using 64KB page granularity working as a
> >> network backend on a non-modified Xen.
> >>
> >> It's only necessary to adapt the ring size and break skb data in small
> >> chunk of 4KB. The rest of the code is relying on the grant table code.
> >>
> >> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> >>
> > 
> > Reviewed-by: Wei Liu <wei.liu2@citrix.com>
> 
> Thank you!
> 
> Regards,
> 
> -- 
> Julien Grall
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#1220699 — Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-08 13:10 +0200
Subject	Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity
Message-ID	<q6oWJ-2qG-3@gated-at.bofh.it>
In reply to	#1220335

Hi Wei,

On 07/09/15 17:57, Wei Liu wrote:
> You might need to rebase you patch. A patch to netback went it recently.

Do you mean 210c34dcd8d912dcc740f1f17625a7293af5cb56 "xen-netback: add
support for multicast control"?

If so I didn't see any specific issue while rebasing on the latest
linus' master.

> On Mon, Sep 07, 2015 at 04:33:56PM +0100, Julien Grall wrote:
>> The PV network protocol is using 4KB page granularity. The goal of this
>> patch is to allow a Linux using 64KB page granularity working as a
>> network backend on a non-modified Xen.
>>
>> It's only necessary to adapt the ring size and break skb data in small
>> chunk of 4KB. The rest of the code is relying on the grant table code.
>>
>> Signed-off-by: Julien Grall <julien.grall@citrix.com>
>>
> 
> Reviewed-by: Wei Liu <wei.liu2@citrix.com>

Thank you!

Regards,

-- 
Julien Grall
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#1223071 — Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-11 21:50 +0200
Subject	Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux
Message-ID	<q7CuC-2YI-23@gated-at.bofh.it>
In reply to	#1220282

Hi,

A quick update on the TODO.

On 07/09/15 16:33, Julien Grall wrote:
> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
> hypercall interface and PV protocol are always based on 4KB page granularity.
> 
> Any attempt to boot a Linux guest with 64KB pages enabled will result to a
> guest crash.
> 
> This series is a first attempt to allow those Linux running with the current
> hypercall interface and PV protocol.
> 
> This solution has been chosen because we want to run Linux 64KB in released
> Xen ARM version or/and platform using an old version of Linux DOM0.
> 
> There is room for improvement, such as support of 64KB grant, modification
> of PV protocol to support different page size... They will be explored in a
> separate patch series later.
> 
> TODO list:
>     - Convert swiotlb to 64KB

Sent http://lists.xen.org/archives/html/xen-devel/2015-09/msg01292.html

>     - Convert xenfb to 64KB
>     - Support for multiple page ring support
>     - Support for 64KB in gnttdev
>     - Support of non-indirect grant with 64KB frontend

Sent http://lists.xen.org/archives/html/xen-devel/2015-09/msg01577.html

>     - It may be possible to move some common define between
>     netback/netfront and blkfront/blkback in an header
> 
> I've got most of the patches for the TODO items. I'm planning to send them as
> a follow-up as it's not a requirement for a basic guests.
> 
> All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
> to run it on x86 as I don't have a box with Xen x86 running. I would be
> happy if someone give a try and see possible regression for x86.
> 
> I know that Konrad as a test-suite for x86. Konrand, would it be possible to
> give a run to for this series?
> 
> A branch based on the latest xentip/for-linus-4.3 can be found here:
> 
> git://xenbits.xen.org/people/julieng/linux-arm.git branch xen-64k-v4

I will resend a new version when 4.3-rc1 is out in order to fix any
possible conflict with linux/master. I already know that the netback
patch (#18) is conflicting with 1d5d48523900a4b0f25d6b52f1a93c84bd671186
"xen-netback: require fewer guest Rx slots when not using GSO".

If the 2 series above are completely acked/reviewed, I will fold them in
this series.

Regards,

-- 
Julien Grall
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#1223945

From	Roger Pau Monné <roger.pau@citrix.com>
Date	2015-09-14 11:00 +0200
Message-ID	<q8xMf-1gc-35@gated-at.bofh.it>
In reply to	#1220282

El 07/09/15 a les 17.33, Julien Grall ha escrit:
> Hi all,
> 
> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
> hypercall interface and PV protocol are always based on 4KB page granularity.
> 
> Any attempt to boot a Linux guest with 64KB pages enabled will result to a
> guest crash.
> 
> This series is a first attempt to allow those Linux running with the current
> hypercall interface and PV protocol.
> 
> This solution has been chosen because we want to run Linux 64KB in released
> Xen ARM version or/and platform using an old version of Linux DOM0.
> 
> There is room for improvement, such as support of 64KB grant, modification
> of PV protocol to support different page size... They will be explored in a
> separate patch series later.
> 
> TODO list:
>     - Convert swiotlb to 64KB
>     - Convert xenfb to 64KB
>     - Support for multiple page ring support
>     - Support for 64KB in gnttdev
>     - Support of non-indirect grant with 64KB frontend
>     - It may be possible to move some common define between
>     netback/netfront and blkfront/blkback in an header
> 
> I've got most of the patches for the TODO items. I'm planning to send them as
> a follow-up as it's not a requirement for a basic guests.
> 
> All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
> to run it on x86 as I don't have a box with Xen x86 running. I would be
> happy if someone give a try and see possible regression for x86.

Do you have figures regarding if/how much performance penalty do the
blkfront/blkback patches add to the traditional 4KB scenario (frontend
and backend running on guests using 4KB pages)?

Since there's been no design document about this and the TODO list
doesn't contain it, I would like to know which plans do we have in order
to fix this properly.

Roger.

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#1224019

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-14 12:50 +0200
Message-ID	<q8zuF-3NA-5@gated-at.bofh.it>
In reply to	#1223945

Hi Roger,

On 14/09/15 09:56, Roger Pau Monné wrote:
> El 07/09/15 a les 17.33, Julien Grall ha escrit:
>> Hi all,
>>
>> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
>> hypercall interface and PV protocol are always based on 4KB page granularity.
>>
>> Any attempt to boot a Linux guest with 64KB pages enabled will result to a
>> guest crash.
>>
>> This series is a first attempt to allow those Linux running with the current
>> hypercall interface and PV protocol.
>>
>> This solution has been chosen because we want to run Linux 64KB in released
>> Xen ARM version or/and platform using an old version of Linux DOM0.
>>
>> There is room for improvement, such as support of 64KB grant, modification
>> of PV protocol to support different page size... They will be explored in a
>> separate patch series later.
>>
>> TODO list:
>>     - Convert swiotlb to 64KB
>>     - Convert xenfb to 64KB
>>     - Support for multiple page ring support
>>     - Support for 64KB in gnttdev
>>     - Support of non-indirect grant with 64KB frontend
>>     - It may be possible to move some common define between
>>     netback/netfront and blkfront/blkback in an header
>>
>> I've got most of the patches for the TODO items. I'm planning to send them as
>> a follow-up as it's not a requirement for a basic guests.
>>
>> All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
>> to run it on x86 as I don't have a box with Xen x86 running. I would be
>> happy if someone give a try and see possible regression for x86.
> 
> Do you have figures regarding if/how much performance penalty do the
> blkfront/blkback patches add to the traditional 4KB scenario (frontend
> and backend running on guests using 4KB pages)?

Which benchmark do you advice? Although, I don't have SSD on this
platform so it may be possible that the bottleneck will be the hard drive.

> 
> Since there's been no design document about this and the TODO list
> doesn't contain it, I would like to know which plans do we have in order
> to fix this properly.

Can you explain what kind of design document you were expecting? The
support of 64KB page granularity is pretty straight-forward and there is
not many way to do it. We have to split the page in 4KB chunk to feed
the ring.

TBH, I'm expecting a small impact to the performance. It would be hard
to get the exactly the same performance as today if we keep the helpers
to avoid the backend dealing himself with the splitting and page
granularity.

Although, if the performance impact is not acceptable, it may be
possible to optimize gnttab_foreach_grant_in_range by moving the
function inline. The current way to the loop is the fastest I've found
(I've wrote a small program to test different way) and we will need it
when different of size will be supported.

Regards,

-- 
Julien Grall
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#1224031

From	Roger Pau Monné <roger.pau@citrix.com>
Date	2015-09-14 13:10 +0200
Message-ID	<q8zO2-4pn-17@gated-at.bofh.it>
In reply to	#1224019

Hello,

El 14/09/15 a les 12.40, Julien Grall ha escrit:
> Hi Roger,
> 
> On 14/09/15 09:56, Roger Pau Monné wrote:
>> El 07/09/15 a les 17.33, Julien Grall ha escrit:
>>> Hi all,
>>>
>>> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
>>> hypercall interface and PV protocol are always based on 4KB page granularity.
>>>
>>> Any attempt to boot a Linux guest with 64KB pages enabled will result to a
>>> guest crash.
>>>
>>> This series is a first attempt to allow those Linux running with the current
>>> hypercall interface and PV protocol.
>>>
>>> This solution has been chosen because we want to run Linux 64KB in released
>>> Xen ARM version or/and platform using an old version of Linux DOM0.
>>>
>>> There is room for improvement, such as support of 64KB grant, modification
>>> of PV protocol to support different page size... They will be explored in a
>>> separate patch series later.
>>>
>>> TODO list:
>>>     - Convert swiotlb to 64KB
>>>     - Convert xenfb to 64KB
>>>     - Support for multiple page ring support
>>>     - Support for 64KB in gnttdev
>>>     - Support of non-indirect grant with 64KB frontend
>>>     - It may be possible to move some common define between
>>>     netback/netfront and blkfront/blkback in an header
>>>
>>> I've got most of the patches for the TODO items. I'm planning to send them as
>>> a follow-up as it's not a requirement for a basic guests.
>>>
>>> All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
>>> to run it on x86 as I don't have a box with Xen x86 running. I would be
>>> happy if someone give a try and see possible regression for x86.
>>
>> Do you have figures regarding if/how much performance penalty do the
>> blkfront/blkback patches add to the traditional 4KB scenario (frontend
>> and backend running on guests using 4KB pages)?
> 
> Which benchmark do you advice? Although, I don't have SSD on this
> platform so it may be possible that the bottleneck will be the hard drive.

I've normally used a ramdisk in order to test performance, but it seems
nullblk would be a better option (it wasn't available before) and it
doesn't reduce the size of RAM available to the system:

https://www.kernel.org/doc/Documentation/block/null_blk.txt

>>
>> Since there's been no design document about this and the TODO list
>> doesn't contain it, I would like to know which plans do we have in order
>> to fix this properly.
> 
> Can you explain what kind of design document you were expecting? The
> support of 64KB page granularity is pretty straight-forward and there is
> not many way to do it. We have to split the page in 4KB chunk to feed
> the ring.

I was thinking about adding support for 64KB grants with the aim of
eventually removing the splitting done in xen-blkfront and the
grant-table code in general.

Some modifications would be needed in xen-blkback in order to support
mapping 64KB grants, but this could also be used by x86 if we ever
enable 2MB grants and allow them to be used in the block PV protocol,
while the current code can only be used by ARM.

> TBH, I'm expecting a small impact to the performance. It would be hard
> to get the exactly the same performance as today if we keep the helpers
> to avoid the backend dealing himself with the splitting and page
> granularity.
> 
> Although, if the performance impact is not acceptable, it may be
> possible to optimize gnttab_foreach_grant_in_range by moving the
> function inline. The current way to the loop is the fastest I've found
> (I've wrote a small program to test different way) and we will need it
> when different of size will be supported.

I don't expect the performance to drop massively with this patches
applied, but it would be good to al least have an idea of the impact.

Roger.

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#1224037

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-14 13:30 +0200
Message-ID	<q8A7n-4LK-1@gated-at.bofh.it>
In reply to	#1224031

On 14/09/15 12:04, Roger Pau Monné wrote:
> Hello,
> 
> El 14/09/15 a les 12.40, Julien Grall ha escrit:
>> Hi Roger,
>>
>> On 14/09/15 09:56, Roger Pau Monné wrote:
>>> El 07/09/15 a les 17.33, Julien Grall ha escrit:
>>>> Hi all,
>>>>
>>>> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
>>>> hypercall interface and PV protocol are always based on 4KB page granularity.
>>>>
>>>> Any attempt to boot a Linux guest with 64KB pages enabled will result to a
>>>> guest crash.
>>>>
>>>> This series is a first attempt to allow those Linux running with the current
>>>> hypercall interface and PV protocol.
>>>>
>>>> This solution has been chosen because we want to run Linux 64KB in released
>>>> Xen ARM version or/and platform using an old version of Linux DOM0.
>>>>
>>>> There is room for improvement, such as support of 64KB grant, modification
>>>> of PV protocol to support different page size... They will be explored in a
>>>> separate patch series later.
>>>>
>>>> TODO list:
>>>>     - Convert swiotlb to 64KB
>>>>     - Convert xenfb to 64KB
>>>>     - Support for multiple page ring support
>>>>     - Support for 64KB in gnttdev
>>>>     - Support of non-indirect grant with 64KB frontend
>>>>     - It may be possible to move some common define between
>>>>     netback/netfront and blkfront/blkback in an header
>>>>
>>>> I've got most of the patches for the TODO items. I'm planning to send them as
>>>> a follow-up as it's not a requirement for a basic guests.
>>>>
>>>> All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
>>>> to run it on x86 as I don't have a box with Xen x86 running. I would be
>>>> happy if someone give a try and see possible regression for x86.
>>>
>>> Do you have figures regarding if/how much performance penalty do the
>>> blkfront/blkback patches add to the traditional 4KB scenario (frontend
>>> and backend running on guests using 4KB pages)?
>>
>> Which benchmark do you advice? Although, I don't have SSD on this
>> platform so it may be possible that the bottleneck will be the hard drive.
> 
> I've normally used a ramdisk in order to test performance, but it seems
> nullblk would be a better option (it wasn't available before) and it
> doesn't reduce the size of RAM available to the system:
> 
> https://www.kernel.org/doc/Documentation/block/null_blk.txt

I will give a look to this.

>>>
>>> Since there's been no design document about this and the TODO list
>>> doesn't contain it, I would like to know which plans do we have in order
>>> to fix this properly.
>>
>> Can you explain what kind of design document you were expecting? The
>> support of 64KB page granularity is pretty straight-forward and there is
>> not many way to do it. We have to split the page in 4KB chunk to feed
>> the ring.
> 
> I was thinking about adding support for 64KB grants with the aim of
> eventually removing the splitting done in xen-blkfront and the
> grant-table code in general.

I'd like to see a basic support of 64KB page granularity upstream before
starting to think about performance improvement. And there is still a
lot to do.

Although, having 64KB grants won't remove the splitting as we would
still have to support frontend/backend which only handle 4KB grant.


>> TBH, I'm expecting a small impact to the performance. It would be hard
>> to get the exactly the same performance as today if we keep the helpers
>> to avoid the backend dealing himself with the splitting and page
>> granularity.
>>
>> Although, if the performance impact is not acceptable, it may be
>> possible to optimize gnttab_foreach_grant_in_range by moving the
>> function inline. The current way to the loop is the fastest I've found
>> (I've wrote a small program to test different way) and we will need it
>> when different of size will be supported.
> 
> I don't expect the performance to drop massively with this patches
> applied, but it would be good to al least have an idea of the impact.

I will only be able to give percentage. I guess this would be sufficient
for you?

Regards,

-- 
Julien Grall
--
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#1224057

From	Roger Pau Monné <roger.pau@citrix.com>
Date	2015-09-14 14:10 +0200
Message-ID	<q8AK7-5JN-27@gated-at.bofh.it>
In reply to	#1224037

El 14/09/15 a les 13.21, Julien Grall ha escrit:
> On 14/09/15 12:04, Roger Pau Monné wrote:
>> Hello,
>>
>> El 14/09/15 a les 12.40, Julien Grall ha escrit:
>>> Hi Roger,
>>>
>>> On 14/09/15 09:56, Roger Pau Monné wrote:
>>>> El 07/09/15 a les 17.33, Julien Grall ha escrit:
>>>>> Hi all,
>>>>>
>>>>> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen
>>>>> hypercall interface and PV protocol are always based on 4KB page granularity.
>>>>>
>>>>> Any attempt to boot a Linux guest with 64KB pages enabled will result to a
>>>>> guest crash.
>>>>>
>>>>> This series is a first attempt to allow those Linux running with the current
>>>>> hypercall interface and PV protocol.
>>>>>
>>>>> This solution has been chosen because we want to run Linux 64KB in released
>>>>> Xen ARM version or/and platform using an old version of Linux DOM0.
>>>>>
>>>>> There is room for improvement, such as support of 64KB grant, modification
>>>>> of PV protocol to support different page size... They will be explored in a
>>>>> separate patch series later.
>>>>>
>>>>> TODO list:
>>>>>     - Convert swiotlb to 64KB
>>>>>     - Convert xenfb to 64KB
>>>>>     - Support for multiple page ring support
>>>>>     - Support for 64KB in gnttdev
>>>>>     - Support of non-indirect grant with 64KB frontend
>>>>>     - It may be possible to move some common define between
>>>>>     netback/netfront and blkfront/blkback in an header
>>>>>
>>>>> I've got most of the patches for the TODO items. I'm planning to send them as
>>>>> a follow-up as it's not a requirement for a basic guests.
>>>>>
>>>>> All patches has been built tested for ARM32, ARM64, x86. But I haven't tested
>>>>> to run it on x86 as I don't have a box with Xen x86 running. I would be
>>>>> happy if someone give a try and see possible regression for x86.
>>>>
>>>> Do you have figures regarding if/how much performance penalty do the
>>>> blkfront/blkback patches add to the traditional 4KB scenario (frontend
>>>> and backend running on guests using 4KB pages)?
>>>
>>> Which benchmark do you advice? Although, I don't have SSD on this
>>> platform so it may be possible that the bottleneck will be the hard drive.
>>
>> I've normally used a ramdisk in order to test performance, but it seems
>> nullblk would be a better option (it wasn't available before) and it
>> doesn't reduce the size of RAM available to the system:
>>
>> https://www.kernel.org/doc/Documentation/block/null_blk.txt
> 
> I will give a look to this.
> 
>>>>
>>>> Since there's been no design document about this and the TODO list
>>>> doesn't contain it, I would like to know which plans do we have in order
>>>> to fix this properly.
>>>
>>> Can you explain what kind of design document you were expecting? The
>>> support of 64KB page granularity is pretty straight-forward and there is
>>> not many way to do it. We have to split the page in 4KB chunk to feed
>>> the ring.
>>
>> I was thinking about adding support for 64KB grants with the aim of
>> eventually removing the splitting done in xen-blkfront and the
>> grant-table code in general.
> 
> I'd like to see a basic support of 64KB page granularity upstream before
> starting to think about performance improvement. And there is still a
> lot to do.

I wasn't actually thinking of this as a performance improvement, but
rather as a way of fixing this properly and removing the complexity
added to xen-blkfront, thus providing a PV block protocol that natively
supports 64KB pages. This would be like hardware components already do
AFAIK, because I don't think there are other drivers in the Linux tree
that do this kind of splitting.

> Although, having 64KB grants won't remove the splitting as we would
> still have to support frontend/backend which only handle 4KB grant.

IMHO, given enough time I would just drop those.

>>> TBH, I'm expecting a small impact to the performance. It would be hard
>>> to get the exactly the same performance as today if we keep the helpers
>>> to avoid the backend dealing himself with the splitting and page
>>> granularity.
>>>
>>> Although, if the performance impact is not acceptable, it may be
>>> possible to optimize gnttab_foreach_grant_in_range by moving the
>>> function inline. The current way to the loop is the fastest I've found
>>> (I've wrote a small program to test different way) and we will need it
>>> when different of size will be supported.
>>
>> I don't expect the performance to drop massively with this patches
>> applied, but it would be good to al least have an idea of the impact.
> 
> I will only be able to give percentage. I guess this would be sufficient
> for you?

Well, absolute numbers together with the standard deviation are IMHO the
best way to provide those figures (ie: see ministat(1) output for
example), but percentages should also be fine.

I'm just interested in knowing the performance difference between having
this patches applied or not when using 4KB pages on the frontend and the
backend.

Roger.
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#1224105

From	Julien Grall <julien.grall@citrix.com>
Date	2015-09-14 14:50 +0200
Message-ID	<q8BmO-6tb-9@gated-at.bofh.it>
In reply to	#1224057

On 14/09/15 13:08, Roger Pau Monné wrote:
>> I'd like to see a basic support of 64KB page granularity upstream before
>> starting to think about performance improvement. And there is still a
>> lot to do.
> 
> I wasn't actually thinking of this as a performance improvement, but
> rather as a way of fixing this properly and removing the complexity
> added to xen-blkfront, thus providing a PV block protocol that natively
> supports 64KB pages. This would be like hardware components already do
> AFAIK, because I don't think there are other drivers in the Linux tree
> that do this kind of splitting.
> 
>> Although, having 64KB grants won't remove the splitting as we would
>> still have to support frontend/backend which only handle 4KB grant.
> 
> IMHO, given enough time I would just drop those.

The PV protocol has always been backward compatible.

Introducing the support of 64KB grant will require some changes in Xen
which won't surely be backported to older version. We still have to be
able to run new Linux guest on older Xen and vice versa.

To give you an example, Centos 7, which will support Xen and only 64KB
page granularity, will be supported for years. Dropping any splitting in
a short future (3-5 years) will just break those guests to boot on Xen.

AFAIK, we never took a such radical decision on Xen based on the
complexity of the code.

Regards,

-- 
Julien Grall
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#1224205

From	Roger Pau Monné <roger.pau@citrix.com>
Date	2015-09-14 16:40 +0200
Message-ID	<q8D5g-xQ-29@gated-at.bofh.it>
In reply to	#1224105

Hello,

El 14/09/15 a les 14.47, Julien Grall ha escrit:
> On 14/09/15 13:08, Roger Pau Monné wrote:
>>> I'd like to see a basic support of 64KB page granularity upstream before
>>> starting to think about performance improvement. And there is still a
>>> lot to do.
>>
>> I wasn't actually thinking of this as a performance improvement, but
>> rather as a way of fixing this properly and removing the complexity
>> added to xen-blkfront, thus providing a PV block protocol that natively
>> supports 64KB pages. This would be like hardware components already do
>> AFAIK, because I don't think there are other drivers in the Linux tree
>> that do this kind of splitting.
>>
>>> Although, having 64KB grants won't remove the splitting as we would
>>> still have to support frontend/backend which only handle 4KB grant.
>>
>> IMHO, given enough time I would just drop those.
> 
> The PV protocol has always been backward compatible.
> 
> Introducing the support of 64KB grant will require some changes in Xen
> which won't surely be backported to older version. We still have to be
> able to run new Linux guest on older Xen and vice versa.

OK, so let's wait a couple of Xen and Linux releases before dropping
this from the Linux kernel once 64KB grant support is added. Guests
should still be able to boot, it's just the disk that won't be attached.

IMHO this splitting is just a workaround for the fact that we don't have
a 64KB PV block protocol, and this is the real problem that should be
solved.

In the long term this will put a burden on all blkfronts (if 64KB pages
are also used by other OSes), while introducing a 64KB PV block protocol
will make the blkfront implementation in all OSes very similar to what
we have now, without replicating the splitting code amongst all the
possible blkfront implementations.

Granted that some changes to blkback will be needed in order to support
mapping 64KB grants, but there are much fewer blkback implementations
out there than blkfronts.

> To give you an example, Centos 7, which will support Xen and only 64KB
> page granularity, will be supported for years. Dropping any splitting in
> a short future (3-5 years) will just break those guests to boot on Xen.

Can't the patches to support 64KB grants be backported to CentOS? In the
past you said that distros had no problem in picking the needed Xen
patches for 64KB support, I don't see how that would be different.

Also, a blkfront with the splitting code should also be able to work
perfectly fine once we have a 64KB PV block protocol, it will just be
treated like it's using 4KB pages, that's all.

> AFAIK, we never took a such radical decision on Xen based on the
> complexity of the code.

We never had to deal with a problem like this I'm afraid (mixing guests
with different page sizes), so I don't think we can make statements
about that.

And it's not just about the complexity, it's because as stated above
this IMHO is just sweeping the real problem under the carpet instead of
solving it.

Roger.

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csiph-web

[PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

Contents

#1220282 — [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

#1220283 — [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux

#1220330 — Re: [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux

#1220288 — [PATCH v4 15/20] block/xen-blkfront: Make it running on 64KB page granularity

#1220289 — [PATCH v4 20/20] arm/xen: Add support for 64KB page granularity

#1220291 — [PATCH v4 17/20] net/xen-netfront: Make it running on 64KB page granularity

#1220293 — [PATCH v4 10/20] xen/xenbus: Use Xen page definition

#1220295 — [PATCH v4 16/20] block/xen-blkback: Make it running on 64KB page granularity

#1220298 — [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

#1220335 — Re: [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

#1220697 — Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

#1220699 — Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity

#1223071 — Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

#1223945

#1224019

#1224031

#1224037

#1224057

#1224105

#1224205