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Re: [PATCH v2 14/20] xen/grant-table: Make it running on 64KB granularity

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  Re: [PATCH v2 14/20] xen/grant-table: Make it running on 64KB  granularity Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-07-16 17:50 +0200
    Re: [Xen-devel] [PATCH v2 14/20] xen/grant-table: Make it running  on 64KB granularity Julien Grall <julien.grall@citrix.com> - 2015-07-16 18:30 +0200
      Re: [Xen-devel] [PATCH v2 14/20] xen/grant-table: Make it running  on 64KB granularity Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-07-17 15:40 +0200

#1186011 — Re: [PATCH v2 14/20] xen/grant-table: Make it running on 64KB granularity

On Thu, 9 Jul 2015, Julien Grall wrote:
> The Xen interface is using 4KB page granularity. This means that each
> grant is 4KB.
> 
> The current implementation allocates a Linux page per grant. On Linux
> using 64KB page granularity, only the first 4KB of the page will be
> used.
> 
> We could decrease the memory wasted by sharing the page with multiple
> grant. It will require some care with the {Set,Clear}ForeignPage macro.
> 
> Note that no changes has been made in the x86 code because both Linux
> and Xen will only use 4KB page granularity.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> Reviewed-by: David Vrabel <david.vrabel@citrix.com>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> ---
>     Changes in v2
>         - Add David's reviewed-by
> ---
>  arch/arm/xen/p2m.c        | 6 +++---
>  drivers/xen/grant-table.c | 6 +++---
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
> index 887596c..0ed01f2 100644
> --- a/arch/arm/xen/p2m.c
> +++ b/arch/arm/xen/p2m.c
> @@ -93,8 +93,8 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
>  	for (i = 0; i < count; i++) {
>  		if (map_ops[i].status)
>  			continue;
> -		set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
> -				    map_ops[i].dev_bus_addr >> PAGE_SHIFT);
> +		set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
> +				    map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT);
>  	}
>  
>  	return 0;
> @@ -108,7 +108,7 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
>  	int i;
>  
>  	for (i = 0; i < count; i++) {
> -		set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
> +		set_phys_to_machine(unmap_ops[i].host_addr >> XEN_PAGE_SHIFT,
>  				    INVALID_P2M_ENTRY);
>  	}
>  
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 3679293..0a1f903 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c

The arm part is fine, but aren't you missing the change to RPP and SPP?


> @@ -668,7 +668,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
>  	if (xen_auto_xlat_grant_frames.count)
>  		return -EINVAL;
>  
> -	vaddr = xen_remap(addr, PAGE_SIZE * max_nr_gframes);
> +	vaddr = xen_remap(addr, XEN_PAGE_SIZE * max_nr_gframes);
>  	if (vaddr == NULL) {
>  		pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!\n",
>  			&addr);
> @@ -680,7 +680,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
>  		return -ENOMEM;
>  	}
>  	for (i = 0; i < max_nr_gframes; i++)
> -		pfn[i] = PFN_DOWN(addr) + i;
> +		pfn[i] = XEN_PFN_DOWN(addr) + i;
>  
>  	xen_auto_xlat_grant_frames.vaddr = vaddr;
>  	xen_auto_xlat_grant_frames.pfn = pfn;
> @@ -1004,7 +1004,7 @@ static void gnttab_request_version(void)
>  {
>  	/* Only version 1 is used, which will always be available. */
>  	grant_table_version = 1;
> -	grefs_per_grant_frame = PAGE_SIZE / sizeof(struct grant_entry_v1);
> +	grefs_per_grant_frame = XEN_PAGE_SIZE / sizeof(struct grant_entry_v1);
>  	gnttab_interface = &gnttab_v1_ops;
>  
>  	pr_info("Grant tables using version %d layout\n", grant_table_version);
> -- 
> 2.1.4
> 
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#1186055 — Re: [Xen-devel] [PATCH v2 14/20] xen/grant-table: Make it running on 64KB granularity

Hi Stefano,

On 16/07/2015 16:47, Stefano Stabellini wrote:
  >> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
>> index 3679293..0a1f903 100644
>> --- a/drivers/xen/grant-table.c
>> +++ b/drivers/xen/grant-table.c
>
> The arm part is fine, but aren't you missing the change to RPP and SPP?

SPP has been removed by commit 548f7c94759ac58d4744ef2663e2a66a106e21c5 
as it was unused.

For RPP, it's used internally so there is no need to switch to 
XEN_PAGE_SIZE. Otherwise we will waste 60KB for each internal page 
allocated (see gnttab_init).

Regards,

-- 
Julien Grall
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#1186829 — Re: [Xen-devel] [PATCH v2 14/20] xen/grant-table: Make it running on 64KB granularity

On Thu, 16 Jul 2015, Julien Grall wrote:
> Hi Stefano,
> 
> On 16/07/2015 16:47, Stefano Stabellini wrote:
>  >> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> > > index 3679293..0a1f903 100644
> > > --- a/drivers/xen/grant-table.c
> > > +++ b/drivers/xen/grant-table.c
> > 
> > The arm part is fine, but aren't you missing the change to RPP and SPP?
> 
> SPP has been removed by commit 548f7c94759ac58d4744ef2663e2a66a106e21c5 as it
> was unused.
> 
> For RPP, it's used internally so there is no need to switch to XEN_PAGE_SIZE.
> Otherwise we will waste 60KB for each internal page allocated (see
> gnttab_init).

I see now that RPP is specifically for internal data structures in
grant-table.c and it is used consistently.

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