Xen devel - Dec 2012 - [PATCH] memop: adjust error checking in populate_physmap()

Checking that multi-page allocations are permitted is unnecessary for
PoD population operations. Instead, the (loop invariant) check added
for addressing XSA-31 can be moved here.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -99,7 +99,8 @@ static void populate_physmap(struct memo
                                      a->nr_extents-1) )
         return;
 
-    if ( !multipage_allocation_permitted(current->domain,
a->extent_order) )
+    if ( a->memflags & MEMF_populate_on_demand ? a->extent_order >
MAX_ORDER :
+         !multipage_allocation_permitted(current->domain,
a->extent_order) )
         return;
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
@@ -115,8 +116,7 @@ static void populate_physmap(struct memo
 
         if ( a->memflags & MEMF_populate_on_demand )
         {
-            if ( a->extent_order > MAX_ORDER ||
-                 guest_physmap_mark_populate_on_demand(d, gpfn,
+            if ( guest_physmap_mark_populate_on_demand(d, gpfn,
                                                        a->extent_order) <
0 )
                 goto out;
         }





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On 06/12/2012 12:54, "Jan Beulich" <JBeulich@suse.com> wrote:
> Checking that multi-page allocations are permitted is unnecessary for
> PoD population operations. Instead, the (loop invariant) check added
> for addressing XSA-31 can be moved here.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -99,7 +99,8 @@ static void populate_physmap(struct memo
>                                       a->nr_extents-1) )
>          return;
>  
> -    if ( !multipage_allocation_permitted(current->domain,
a->extent_order) )
> +    if ( a->memflags & MEMF_populate_on_demand ? a->extent_order
> MAX_ORDER
> :
> +         !multipage_allocation_permitted(current->domain,
a->extent_order) )
>          return;
>  
>      for ( i = a->nr_done; i < a->nr_extents; i++ )
> @@ -115,8 +116,7 @@ static void populate_physmap(struct memo
>  
>          if ( a->memflags & MEMF_populate_on_demand )
>          {
> -            if ( a->extent_order > MAX_ORDER ||
> -                 guest_physmap_mark_populate_on_demand(d, gpfn,
> +            if ( guest_physmap_mark_populate_on_demand(d, gpfn,
>                                                         a->extent_order)
< 0 )
>                  goto out;
>          }
> 
> 
> 
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