KVM: X86: Synchronize the shadow pagetable before link it

[mirror_ubuntu-jammy-kernel.git] / arch / x86 / kvm / mmu / paging_tmpl.h

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index efce0a935e2312bd51cf9c365f2d664d96e0c6a0..913d52a7923e654576b1af8ad0400a55cd36e86a 100644 (file)
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -707,8 +707,27 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gpa_t addr,
                if (!is_shadow_present_pte(*it.sptep)) {
                        table_gfn = gw->table_gfn[it.level - 2];
                        access = gw->pt_access[it.level - 2];
-                       sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1,
-                                             false, access);
+                       sp = kvm_mmu_get_page(vcpu, table_gfn, addr,
+                                             it.level-1, false, access);
+                       /*
+                        * We must synchronize the pagetable before linking it
+                        * because the guest doesn't need to flush tlb when
+                        * the gpte is changed from non-present to present.
+                        * Otherwise, the guest may use the wrong mapping.
+                        *
+                        * For PG_LEVEL_4K, kvm_mmu_get_page() has already
+                        * synchronized it transiently via kvm_sync_page().
+                        *
+                        * For higher level pagetable, we synchronize it via
+                        * the slower mmu_sync_children().  If it needs to
+                        * break, some progress has been made; return
+                        * RET_PF_RETRY and retry on the next #PF.
+                        * KVM_REQ_MMU_SYNC is not necessary but it
+                        * expedites the process.
+                        */
+                       if (sp->unsync_children &&
+                           mmu_sync_children(vcpu, sp, false))
+                               return RET_PF_RETRY;
                }
 
                /*