KVM: MMU: propagate alloc_workqueue failure

If kvm->arch.tdp_mmu_zap_wq cannot be created, the failure has
to be propagated up to kvm_mmu_init_vm and kvm_arch_init_vm.
kvm_arch_init_vm also has to undo all the initialization, so
group all the MMU initialization code at the beginning and
handle cleaning up of kvm_page_track_init.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1584,7 +1584,7 @@ void kvm_mmu_module_exit(void);
 
 void kvm_mmu_destroy(struct kvm_vcpu *vcpu);
 int kvm_mmu_create(struct kvm_vcpu *vcpu);
-void kvm_mmu_init_vm(struct kvm *kvm);
+int kvm_mmu_init_vm(struct kvm *kvm);
 void kvm_mmu_uninit_vm(struct kvm *kvm);
 
 void kvm_mmu_after_set_cpuid(struct kvm_vcpu *vcpu);

arch/x86/kvm/mmu/mmu.c

@@ -5768,17 +5768,24 @@ static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
 	kvm_mmu_zap_all_fast(kvm);
 }
 
-void kvm_mmu_init_vm(struct kvm *kvm)
+int kvm_mmu_init_vm(struct kvm *kvm)
 {
 	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
+	int r;
 
+	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
+	INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
+	INIT_LIST_HEAD(&kvm->arch.lpage_disallowed_mmu_pages);
 	spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
 
-	kvm_mmu_init_tdp_mmu(kvm);
+	r = kvm_mmu_init_tdp_mmu(kvm);
+	if (r < 0)
+		return r;
 
 	node->track_write = kvm_mmu_pte_write;
 	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
 	kvm_page_track_register_notifier(kvm, node);
+	return 0;
 }
 
 void kvm_mmu_uninit_vm(struct kvm *kvm)

arch/x86/kvm/mmu/tdp_mmu.c

@@ -14,21 +14,24 @@ static bool __read_mostly tdp_mmu_enabled = true;
 module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0644);
 
 /* Initializes the TDP MMU for the VM, if enabled. */
-bool kvm_mmu_init_tdp_mmu(struct kvm *kvm)
+int kvm_mmu_init_tdp_mmu(struct kvm *kvm)
 {
+	struct workqueue_struct *wq;
+
 	if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled))
-		return false;
+		return 0;
+
+	wq = alloc_workqueue("kvm", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 0);
+	if (!wq)
+		return -ENOMEM;
 
 	/* This should not be changed for the lifetime of the VM. */
 	kvm->arch.tdp_mmu_enabled = true;
-
 	INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots);
 	spin_lock_init(&kvm->arch.tdp_mmu_pages_lock);
 	INIT_LIST_HEAD(&kvm->arch.tdp_mmu_pages);
-	kvm->arch.tdp_mmu_zap_wq =
-		alloc_workqueue("kvm", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 0);
-
-	return true;
+	kvm->arch.tdp_mmu_zap_wq = wq;
+	return 1;
 }
 
 /* Arbitrarily returns true so that this may be used in if statements. */

arch/x86/kvm/mmu/tdp_mmu.h

@@ -72,7 +72,7 @@ u64 *kvm_tdp_mmu_fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, u64 addr,
 					u64 *spte);
 
 #ifdef CONFIG_X86_64
-bool kvm_mmu_init_tdp_mmu(struct kvm *kvm);
+int kvm_mmu_init_tdp_mmu(struct kvm *kvm);
 void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm);
 static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; }
 
@@ -93,7 +93,7 @@ static inline bool is_tdp_mmu(struct kvm_mmu *mmu)
 	return sp && is_tdp_mmu_page(sp) && sp->root_count;
 }
 #else
-static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; }
+static inline int kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return 0; }
 static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {}
 static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; }
 static inline bool is_tdp_mmu(struct kvm_mmu *mmu) { return false; }

arch/x86/kvm/x86.c

@@ -11629,12 +11629,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	ret = kvm_page_track_init(kvm);
 	if (ret)
-		return ret;
+		goto out;
+
+	ret = kvm_mmu_init_vm(kvm);
+	if (ret)
+		goto out_page_track;
 
 	INIT_HLIST_HEAD(&kvm->arch.mask_notifier_list);
-	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
-	INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
-	INIT_LIST_HEAD(&kvm->arch.lpage_disallowed_mmu_pages);
 	INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);
 	atomic_set(&kvm->arch.noncoherent_dma_count, 0);
 
@@ -11666,10 +11667,14 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	kvm_apicv_init(kvm);
 	kvm_hv_init_vm(kvm);
-	kvm_mmu_init_vm(kvm);
 	kvm_xen_init_vm(kvm);
 
 	return static_call(kvm_x86_vm_init)(kvm);
+
+out_page_track:
+	kvm_page_track_cleanup(kvm);
+out:
+	return ret;
 }
 
 int kvm_arch_post_init_vm(struct kvm *kvm)