KVM: MMU: cleanup __kvm_sync_page and its callers

Calling kvm_unlink_unsync_page in the middle of __kvm_sync_page makes
things unnecessarily tricky.  If kvm_mmu_prepare_zap_page is called,
it will call kvm_unlink_unsync_page too.  So kvm_unlink_unsync_page can
be called just as well at the beginning or the end of __kvm_sync_page...
which means that we might do it in kvm_sync_page too and remove the
parameter.

kvm_sync_page ends up being the same code that kvm_sync_pages used
to have before the previous patch.
Reviewed-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

@@ -1917,16 +1917,13 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
 
 /* @sp->gfn should be write-protected at the call site */
 static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
-			   struct list_head *invalid_list, bool clear_unsync)
+			   struct list_head *invalid_list)
 {
 	if (sp->role.cr4_pae != !!is_pae(vcpu)) {
 		kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
 		return 1;
 	}
 
-	if (clear_unsync)
-		kvm_unlink_unsync_page(vcpu->kvm, sp);
-
 	if (vcpu->arch.mmu.sync_page(vcpu, sp)) {
 		kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
 		return 1;
@@ -1956,7 +1953,7 @@ static int kvm_sync_page_transient(struct kvm_vcpu *vcpu,
 	LIST_HEAD(invalid_list);
 	int ret;
 
-	ret = __kvm_sync_page(vcpu, sp, &invalid_list, false);
+	ret = __kvm_sync_page(vcpu, sp, &invalid_list);
 	kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, !ret);
 
 	return ret;
@@ -1972,7 +1969,8 @@ static void mmu_audit_disable(void) { }
 static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 			 struct list_head *invalid_list)
 {
-	return __kvm_sync_page(vcpu, sp, invalid_list, true);
+	kvm_unlink_unsync_page(vcpu->kvm, sp);
+	return __kvm_sync_page(vcpu, sp, invalid_list);
 }
 
 /* @gfn should be write-protected at the call site */