[Xen-devel] [PATCH MM-PART3 v2 04/12] xen/arm: mm: Only increment mfn when valid in xen_pt_update

[Julien Grall <julien.grall@xxxxxxx>]

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@xxxxxxx>
Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>

---
    Changes in v2:
        - Move the patch earlier on in the series
        - Add Andrii's reviewed-by
---
 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 f956aa6399..9de2a1150f 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1051,11 +1051,14 @@ 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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