KVM: Convert KVM_ARCH_WANT_MMU_NOTIFIER to CONFIG_KVM_GENERIC_MMU_NOTIFIER

Convert KVM_ARCH_WANT_MMU_NOTIFIER into a Kconfig and select it where
appropriate to effectively maintain existing behavior.  Using a proper
Kconfig will simplify building more functionality on top of KVM's
mmu_notifier infrastructure.

Add a forward declaration of kvm_gfn_range to kvm_types.h so that
including arch/powerpc/include/asm/kvm_ppc.h's with CONFIG_KVM=n doesn't
generate warnings due to kvm_gfn_range being undeclared.  PPC defines
hooks for PR vs. HV without guarding them via #ifdeffery, e.g.

  bool (*unmap_gfn_range)(struct kvm *kvm, struct kvm_gfn_range *range);
  bool (*age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
  bool (*test_age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
  bool (*set_spte_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);

Alternatively, PPC could forward declare kvm_gfn_range, but there's no
good reason not to define it in common KVM.
Acked-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Message-Id: <20231027182217.3615211-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/arm64/include/asm/kvm_host.h

@@ -954,8 +954,6 @@ int __kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
 int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 			      struct kvm_vcpu_events *events);
 
-#define KVM_ARCH_WANT_MMU_NOTIFIER
-
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 

arch/arm64/kvm/Kconfig

@@ -22,7 +22,7 @@ menuconfig KVM
 	bool "Kernel-based Virtual Machine (KVM) support"
 	depends on HAVE_KVM
 	select KVM_GENERIC_HARDWARE_ENABLING
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	select PREEMPT_NOTIFIERS
 	select HAVE_KVM_CPU_RELAX_INTERCEPT
 	select KVM_MMIO

arch/loongarch/include/asm/kvm_host.h

@@ -183,7 +183,6 @@ void kvm_flush_tlb_all(void);
 void kvm_flush_tlb_gpa(struct kvm_vcpu *vcpu, unsigned long gpa);
 int kvm_handle_mm_fault(struct kvm_vcpu *vcpu, unsigned long badv, bool write);
 
-#define KVM_ARCH_WANT_MMU_NOTIFIER
 void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end, bool blockable);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);

arch/loongarch/kvm/Kconfig

@@ -26,9 +26,9 @@ config KVM
 	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_GENERIC_HARDWARE_ENABLING
+	select KVM_GENERIC_MMU_NOTIFIER
 	select KVM_MMIO
 	select KVM_XFER_TO_GUEST_WORK
-	select MMU_NOTIFIER
 	select PREEMPT_NOTIFIERS
 	help
 	  Support hosting virtualized guest machines using

arch/mips/include/asm/kvm_host.h

@@ -810,8 +810,6 @@ int kvm_mips_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn);
 pgd_t *kvm_pgd_alloc(void);
 void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
 
-#define KVM_ARCH_WANT_MMU_NOTIFIER
-
 /* Emulation */
 enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause);
 int kvm_get_badinstr(u32 *opc, struct kvm_vcpu *vcpu, u32 *out);

arch/mips/kvm/Kconfig

@@ -25,7 +25,7 @@ config KVM
 	select HAVE_KVM_EVENTFD
 	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select KVM_MMIO
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	select INTERVAL_TREE
 	select KVM_GENERIC_HARDWARE_ENABLING
 	help

arch/powerpc/include/asm/kvm_host.h

@@ -62,8 +62,6 @@
 
 #include <linux/mmu_notifier.h>
 
-#define KVM_ARCH_WANT_MMU_NOTIFIER
-
 #define HPTEG_CACHE_NUM			(1 << 15)
 #define HPTEG_HASH_BITS_PTE		13
 #define HPTEG_HASH_BITS_PTE_LONG	12

arch/powerpc/kvm/Kconfig

@@ -42,7 +42,7 @@ config KVM_BOOK3S_64_HANDLER
 config KVM_BOOK3S_PR_POSSIBLE
 	bool
 	select KVM_MMIO
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 
 config KVM_BOOK3S_HV_POSSIBLE
 	bool
@@ -85,7 +85,7 @@ config KVM_BOOK3S_64_HV
 	tristate "KVM for POWER7 and later using hypervisor mode in host"
 	depends on KVM_BOOK3S_64 && PPC_POWERNV
 	select KVM_BOOK3S_HV_POSSIBLE
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	select CMA
 	help
 	  Support running unmodified book3s_64 guest kernels in
@@ -194,7 +194,7 @@ config KVM_E500V2
 	depends on !CONTEXT_TRACKING_USER
 	select KVM
 	select KVM_MMIO
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	help
 	  Support running unmodified E500 guest kernels in virtual machines on
 	  E500v2 host processors.
@@ -211,7 +211,7 @@ config KVM_E500MC
 	select KVM
 	select KVM_MMIO
 	select KVM_BOOKE_HV
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	help
 	  Support running unmodified E500MC/E5500/E6500 guest kernels in
 	  virtual machines on E500MC/E5500/E6500 host processors.

arch/powerpc/kvm/powerpc.c

@@ -632,9 +632,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		break;
 #endif
 	case KVM_CAP_SYNC_MMU:
-#if !defined(CONFIG_MMU_NOTIFIER) || !defined(KVM_ARCH_WANT_MMU_NOTIFIER)
-		BUILD_BUG();
-#endif
+		BUILD_BUG_ON(!IS_ENABLED(CONFIG_KVM_GENERIC_MMU_NOTIFIER));
 		r = 1;
 		break;
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

arch/riscv/include/asm/kvm_host.h

@@ -267,8 +267,6 @@ struct kvm_vcpu_arch {
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 
-#define KVM_ARCH_WANT_MMU_NOTIFIER
-
 #define KVM_RISCV_GSTAGE_TLB_MIN_ORDER		12
 
 void kvm_riscv_local_hfence_gvma_vmid_gpa(unsigned long vmid,

arch/riscv/kvm/Kconfig

@@ -30,7 +30,7 @@ config KVM
 	select KVM_GENERIC_HARDWARE_ENABLING
 	select KVM_MMIO
 	select KVM_XFER_TO_GUEST_WORK
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	select PREEMPT_NOTIFIERS
 	help
 	  Support hosting virtualized guest machines.

arch/x86/include/asm/kvm_host.h

@@ -2141,8 +2141,6 @@ enum {
 # define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, 0)
 #endif
 
-#define KVM_ARCH_WANT_MMU_NOTIFIER
-
 int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v);
 int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu);
 int kvm_cpu_has_extint(struct kvm_vcpu *v);

arch/x86/kvm/Kconfig

@@ -24,7 +24,7 @@ config KVM
 	depends on HIGH_RES_TIMERS
 	depends on X86_LOCAL_APIC
 	select PREEMPT_NOTIFIERS
-	select MMU_NOTIFIER
+	select KVM_GENERIC_MMU_NOTIFIER
 	select HAVE_KVM_IRQCHIP
 	select HAVE_KVM_PFNCACHE
 	select HAVE_KVM_IRQFD

include/linux/kvm_host.h

@@ -253,7 +253,7 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
 #endif
 
-#ifdef KVM_ARCH_WANT_MMU_NOTIFIER
+#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 union kvm_mmu_notifier_arg {
 	pte_t pte;
 };
@@ -783,7 +783,7 @@ struct kvm {
 	struct hlist_head irq_ack_notifier_list;
 #endif
 
-#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 	struct mmu_notifier mmu_notifier;
 	unsigned long mmu_invalidate_seq;
 	long mmu_invalidate_in_progress;
@@ -1946,7 +1946,7 @@ extern const struct _kvm_stats_desc kvm_vm_stats_desc[];
 extern const struct kvm_stats_header kvm_vcpu_stats_header;
 extern const struct _kvm_stats_desc kvm_vcpu_stats_desc[];
 
-#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 static inline int mmu_invalidate_retry(struct kvm *kvm, unsigned long mmu_seq)
 {
 	if (unlikely(kvm->mmu_invalidate_in_progress))

include/linux/kvm_types.h

@@ -6,6 +6,7 @@
 struct kvm;
 struct kvm_async_pf;
 struct kvm_device_ops;
+struct kvm_gfn_range;
 struct kvm_interrupt;
 struct kvm_irq_routing_table;
 struct kvm_memory_slot;

virt/kvm/Kconfig

@@ -92,3 +92,7 @@ config HAVE_KVM_PM_NOTIFIER
 
 config KVM_GENERIC_HARDWARE_ENABLING
        bool
+
+config KVM_GENERIC_MMU_NOTIFIER
+       select MMU_NOTIFIER
+       bool

virt/kvm/kvm_main.c

@@ -535,7 +535,7 @@ void kvm_destroy_vcpus(struct kvm *kvm)
 }
 EXPORT_SYMBOL_GPL(kvm_destroy_vcpus);
 
-#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
 {
 	return container_of(mn, struct kvm, mmu_notifier);
@@ -962,14 +962,14 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
 	return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
 }
 
-#else  /* !(CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER) */
+#else  /* !CONFIG_KVM_GENERIC_MMU_NOTIFIER */
 
 static int kvm_init_mmu_notifier(struct kvm *kvm)
 {
 	return 0;
 }
 
-#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
+#endif /* CONFIG_KVM_GENERIC_MMU_NOTIFIER */
 
 #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
 static int kvm_pm_notifier_call(struct notifier_block *bl,
@@ -1289,7 +1289,7 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
 out_err_no_debugfs:
 	kvm_coalesced_mmio_free(kvm);
 out_no_coalesced_mmio:
-#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 	if (kvm->mmu_notifier.ops)
 		mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
 #endif
@@ -1349,7 +1349,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
 		kvm->buses[i] = NULL;
 	}
 	kvm_coalesced_mmio_free(kvm);
-#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+#ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 	mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
 	/*
 	 * At this point, pending calls to invalidate_range_start()