[COMMIT master] KVM: MMU: unalias gfn before sp->gfns[] comparison in sync_page

[Avi Kivity]

From: Xiao Guangrong <xiaoguangr...@cn.fujitsu.com>

sp->gfns[] contain unaliased gfns, but gpte might contain pointer
to aliased region.

Signed-off-by: Xiao Guangrong <xiaoguangr...@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 11d8a16..71c73fe 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -588,7 +588,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct 
kvm_mmu_page *sp)
                unsigned pte_access;
                pt_element_t gpte;
                gpa_t pte_gpa;
-               gfn_t gfn = sp->gfns[i];
+               gfn_t gfn;
 
                if (!is_shadow_present_pte(sp->spt[i]))
                        continue;
@@ -599,8 +599,9 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct 
kvm_mmu_page *sp)
                                          sizeof(pt_element_t)))
                        return -EINVAL;
 
-               if (gpte_to_gfn(gpte) != gfn || !is_present_gpte(gpte) ||
-                   !(gpte & PT_ACCESSED_MASK)) {
+               gfn = gpte_to_gfn(gpte);
+               if (unalias_gfn(vcpu->kvm, gfn) != sp->gfns[i] ||
+                     !is_present_gpte(gpte) || !(gpte & PT_ACCESSED_MASK)) {
                        u64 nonpresent;
 
                        rmap_remove(vcpu->kvm, &sp->spt[i]);
--
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