KVM: x86/mmu: Consolidate kvm_mmu_zap_all() and kvm_mmu_zap_mmio_sptes()

...via a new helper, __kvm_mmu_zap_all().  An alternative to passing a
'bool mmio_only' would be to pass a callback function to filter the
shadow page, i.e. to make __kvm_mmu_zap_all() generic and reusable, but
zapping all shadow pages is a last resort, i.e. making the helper less
extensible is a feature of sorts.  And the explicit MMIO parameter makes
it easy to preserve the WARN_ON_ONCE() if a restart is triggered when
zapping MMIO sptes.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

@@ -5840,7 +5840,7 @@ void kvm_mmu_slot_set_dirty(struct kvm *kvm,
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty);
 
-void kvm_mmu_zap_all(struct kvm *kvm)
+static void __kvm_mmu_zap_all(struct kvm *kvm, bool mmio_only)
 {
 	struct kvm_mmu_page *sp, *node;
 	LIST_HEAD(invalid_list);
@@ -5849,30 +5849,12 @@ void kvm_mmu_zap_all(struct kvm *kvm)
 	spin_lock(&kvm->mmu_lock);
 restart:
 	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
-		if (sp->role.invalid && sp->root_count)
+		if (mmio_only && !sp->mmio_cached)
 			continue;
-		if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign) ||
-		    cond_resched_lock(&kvm->mmu_lock))
-			goto restart;
-	}
-
-	kvm_mmu_commit_zap_page(kvm, &invalid_list);
-	spin_unlock(&kvm->mmu_lock);
-}
-
-static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
-{
-	struct kvm_mmu_page *sp, *node;
-	LIST_HEAD(invalid_list);
-	int ign;
-
-	spin_lock(&kvm->mmu_lock);
-restart:
-	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
-		if (!sp->mmio_cached)
+		if (sp->role.invalid && sp->root_count)
 			continue;
 		if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign)) {
-			WARN_ON_ONCE(1);
+			WARN_ON_ONCE(mmio_only);
 			goto restart;
 		}
 		if (cond_resched_lock(&kvm->mmu_lock))
@@ -5883,6 +5865,11 @@ static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
 	spin_unlock(&kvm->mmu_lock);
 }
 
+void kvm_mmu_zap_all(struct kvm *kvm)
+{
+	return __kvm_mmu_zap_all(kvm, false);
+}
+
 void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
 {
 	WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
@@ -5904,7 +5891,7 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
 	 */
 	if (unlikely(gen == 0)) {
 		kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
-		kvm_mmu_zap_mmio_sptes(kvm);
+		__kvm_mmu_zap_all(kvm, true);
 	}
 }