[v1] xen/arm: Provide a generic function to update Xen PT

[Xen-devel] [PATCH 05/12] xen/arm: mm: Only increment mfn when valid in xen_pt_update

Posted by Julien Grall 6 years, 9 months ago

Currently, the MFN will be incremented even if it is invalid. This will
result to have a valid MFN after the first iteration.

While this is not a major problem today, this will be in the future if
the code expect an invalid MFN at every iteration.

Such behavior is prevented by avoiding to increment an invalid MFN.

Signed-off-by: Julien Grall <julien.grall@arm.com>
---
 xen/arch/arm/mm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index b61217abd0..eee7122c88 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1046,11 +1046,14 @@ static int xen_pt_update(enum xenmap_operation op,
 
     spin_lock(&xen_pt_lock);
 
-    for(; addr < addr_end; addr += PAGE_SIZE, mfn = mfn_add(mfn, 1))
+    for( ; addr < addr_end; addr += PAGE_SIZE )
     {
         rc = xen_pt_update_entry(op, addr, mfn, flags);
         if ( rc )
             break;
+
+        if ( !mfn_eq(mfn, INVALID_MFN) )
+            mfn = mfn_add(mfn, 1);
     }
 
     /*
-- 
2.11.0


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Re: [Xen-devel] [PATCH 05/12] xen/arm: mm: Only increment mfn when valid in xen_pt_update

Posted by Andrii Anisov 6 years, 9 months ago


On 24.04.19 19:59, Julien Grall wrote:
> Currently, the MFN will be incremented even if it is invalid. This will
> result to have a valid MFN after the first iteration.
> 
> While this is not a major problem today, this will be in the future if
> the code expect an invalid MFN at every iteration.
> 
> Such behavior is prevented by avoiding to increment an invalid MFN.
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>

Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>

-- 
Sincerely,
Andrii Anisov.

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