kvm: x86: Skip shadow page resync on CR3 switch when indicated by guest

When the guest indicates that the TLB doesn't need to be flushed in a
CR3 switch, we can also skip resyncing the shadow page tables since an
out-of-sync shadow page table is equivalent to an out-of-sync TLB.

Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -858,10 +858,10 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 #endif
 
 	if (cr3 == kvm_read_cr3(vcpu) && !pdptrs_changed(vcpu)) {
-		kvm_mmu_sync_roots(vcpu);
-
-		if (!skip_tlb_flush)
+		if (!skip_tlb_flush) {
+			kvm_mmu_sync_roots(vcpu);
 			kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
+		}
 		return 0;
 	}