[PATCH] x86/shadow: correct GFN use by sh_unshadow_for_p2m_change()

[PATCH] x86/shadow: correct GFN use by sh_unshadow_for_p2m_change()

[Jan Beulich]

Luckily sh_remove_all_mappings()'s use of the parameter is limited to
generation of log messages. Nevertheless we'd better pass correct GFNs
around:
- the incoming GFN, when replacing a large page, may not be large page
  aligned,
- incrementing by page-size-scaled values can't be right.

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

--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -3115,6 +3115,8 @@ static void sh_unshadow_for_p2m_change(s
                  && mfn_valid(nmfn) )
                 npte = map_domain_page(nmfn);
 
+            gfn &= ~(L1_PAGETABLE_ENTRIES - 1);
+
             for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
             {
                 if ( !npte
@@ -3123,8 +3125,7 @@ static void sh_unshadow_for_p2m_change(s
                 {
                     /* This GFN->MFN mapping has gone away */
                     sh_remove_all_shadows_and_parents(d, omfn);
-                    if ( sh_remove_all_mappings(d, omfn,
-                                                _gfn(gfn + (i << PAGE_SHIFT))) )
+                    if ( sh_remove_all_mappings(d, omfn, _gfn(gfn + i)) )
                         cpumask_or(&flushmask, &flushmask, d->dirty_cpumask);
                 }
                 omfn = mfn_add(omfn, 1);

Re: [PATCH] x86/shadow: correct GFN use by sh_unshadow_for_p2m_change()

[Tim Deegan]

At 16:42 +0100 on 28 Oct (1603903365), Jan Beulich wrote:
> Luckily sh_remove_all_mappings()'s use of the parameter is limited to
> generation of log messages. Nevertheless we'd better pass correct GFNs
> around:
> - the incoming GFN, when replacing a large page, may not be large page
>   aligned,
> - incrementing by page-size-scaled values can't be right.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Tim Deegan <tim@xen.org>

Thanks!

Tim.