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Groups > linux.kernel > #1236146

[PATCH v5 16/22] block/xen-blkback: Make it running on 64KB page granularity

From Julien Grall <julien.grall@citrix.com>
Newsgroups linux.kernel
Subject [PATCH v5 16/22] block/xen-blkback: Make it running on 64KB page granularity
Date 2015-09-30 13:00 +0200
Message-ID <qenh8-2Ko-15@gated-at.bofh.it> (permalink)
References <qen7r-2yO-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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 6a685ae..809634c 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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Thread

[PATCH v5 00/22] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-30 12:50 +0200
  [PATCH v5 02/22] arm/xen: Drop pte_mfn and mfn_pte Julien Grall <julien.grall@citrix.com> - 2015-09-30 12:50 +0200
  [PATCH v5 07/22] block/xen-blkfront: Store a page rather a pfn in the grant structure Julien Grall <julien.grall@citrix.com> - 2015-09-30 12:50 +0200
  [PATCH v5 09/22] xen/biomerge: Don't allow biovec's to be merged when Linux is not using 4KB pages Julien Grall <julien.grall@citrix.com> - 2015-09-30 12:50 +0200
  [PATCH v5 20/22] arm/xen: Add support for 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 10/22] xen/xenbus: Use Xen page definition Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 16/22] block/xen-blkback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 11/22] tty/hvc: xen: Use xen page definition Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 22/22] xen/swiotlb: Add support for 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 19/22] xen/privcmd: Add support for Linux 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 17/22] net/xen-netfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 14/22] xen/grant-table: Make it running on 64KB granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 12/22] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
    Re: [PATCH v5 12/22] xen/balloon: Don't rely on the page granularity  is the same for Xen and Linux David Vrabel <david.vrabel@citrix.com> - 2015-10-02 16:10 +0200
      Re: [PATCH v5 12/22] xen/balloon: Don't rely on the page granularity  is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-10-02 16:40 +0200
        Re: [PATCH v5 12/22] xen/balloon: Don't rely on the page granularity  is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-10-02 17:00 +0200
          Re: [PATCH v5 12/22] xen/balloon: Don't rely on the page granularity  is the same for Xen and Linux Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-10-02 17:20 +0200
          Re: [Xen-devel] [PATCH v5 12/22] xen/balloon: Don't rely on the page  granularity is the same for Xen and Linux David Vrabel <david.vrabel@citrix.com> - 2015-10-02 17:20 +0200
  [PATCH v5 15/22] block/xen-blkfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 13/22] xen/events: fifo: Make it running on 64KB granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 21/22] xen/swiotlb: Pass addresses rather than frame numbers to xen_arch_need_swiotlb Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  [PATCH v5 18/22] net/xen-netback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200
  Re: [PATCH v5 00/22] xen/arm64: Add support for 64KB page in Linux Mark Rutland <mark.rutland@arm.com> - 2015-09-30 13:40 +0200
    Re: [PATCH v5 00/22] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:50 +0200
      Re: [PATCH v5 00/22] xen/arm64: Add support for 64KB page in Linux Mark Rutland <mark.rutland@arm.com> - 2015-09-30 15:10 +0200
  Re: [Xen-devel] [PATCH v5 00/22] xen/arm64: Add support for 64KB  page in Linux David Vrabel <david.vrabel@citrix.com> - 2015-10-01 17:20 +0200

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