KVM: MMU: Avoid dropping accessed bit while removing write access

One more "KVM: MMU: Don't drop accessed bit while updating an spte."

Sptes are accessed by both kvm and hardware.
This patch uses update_spte() to fix the way of removing write access.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -3447,7 +3447,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
 		for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
 			/* avoid RMW */
 			if (is_writable_pte(pt[i]))
-				pt[i] &= ~PT_WRITABLE_MASK;
+				update_spte(&pt[i], pt[i] & ~PT_WRITABLE_MASK);
 	}
 	kvm_flush_remote_tlbs(kvm);
 }