[PATCH V2] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

[PATCH V2] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

[Peng Fan]

On ARM64, "frametable_size >> SECOND_SHIFT" computes the number
of second level entries, not the number of second level pages.

"ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT" which computes
the number of the first level entries (the number of second level pages),
is the correct one that should be used.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
---

V2:
 Take Julien's suggestion in http://lists.xen.org/archives/html/xen-devel/2016-05/msg01145.html.
 Refine commit log.

 xen/arch/arm/mm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 0a4f845..5f60aa4 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -767,7 +767,8 @@ void __init setup_frametable_mappings(paddr_t ps, paddr_t pe)
     base_mfn = alloc_boot_pages(frametable_size >> PAGE_SHIFT, 32<<(20-12));
 
 #ifdef CONFIG_ARM_64
-    nr_second = frametable_size >> SECOND_SHIFT;
+    /* Compute the number of second level pages. */
+    nr_second = ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT;
     second_base = alloc_boot_pages(nr_second, 1);
     second = mfn_to_virt(second_base);
     for ( i = 0; i < nr_second; i++ )
-- 
2.6.2


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Re: [PATCH V2] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

[Julien Grall]

(CC Wei for Xen 4.7)

Hi,

On 12/05/16 14:03, Peng Fan wrote:
> On ARM64, "frametable_size >> SECOND_SHIFT" computes the number
> of second level entries, not the number of second level pages.
>
> "ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT" which computes
> the number of the first level entries (the number of second level pages),
> is the correct one that should be used.
>
> Signed-off-by: Peng Fan <van.freenix@gmail.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Julien Grall <julien.grall@arm.com>

Reviewed-by: Julien Grall <julien.grall@arm.com>

This is a bug fix for Xen 4.7 and should be backported up to Xen 4.4.

Wei, could we get a release-ack for this patch?

The computation of the number of page to allocation was wrong. This 
could result to overrun xen_first on platform with big amount of memory.

Regards,

-- 
Julien Grall

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Re: [PATCH V2] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

[Wei Liu]

On Mon, May 16, 2016 at 10:36:11AM +0100, Julien Grall wrote:
> (CC Wei for Xen 4.7)
> 
> Hi,
> 
> On 12/05/16 14:03, Peng Fan wrote:
> >On ARM64, "frametable_size >> SECOND_SHIFT" computes the number
> >of second level entries, not the number of second level pages.
> >
> >"ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT" which computes
> >the number of the first level entries (the number of second level pages),
> >is the correct one that should be used.
> >
> >Signed-off-by: Peng Fan <van.freenix@gmail.com>
> >Cc: Stefano Stabellini <sstabellini@kernel.org>
> >Cc: Julien Grall <julien.grall@arm.com>
> 
> Reviewed-by: Julien Grall <julien.grall@arm.com>

Release-acked-by: Wei Liu <wei.liu2@citrix.com>

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