kvm: x86: Introduce APICv inhibit reason bits

There are several reasons in which a VM needs to deactivate APICv
e.g. disable APICv via parameter during module loading, or when
enable Hyper-V SynIC support. Additional inhibit reasons will be
introduced later on when dynamic APICv is supported,

Introduce KVM APICv inhibit reason bits along with a new variable,
apicv_inhibit_reasons, to help keep track of APICv state for each VM,

Initially, the APICV_INHIBIT_REASON_DISABLE bit is used to indicate
the case where APICv is disabled during KVM module load.
(e.g. insmod kvm_amd avic=0 or insmod kvm_intel enable_apicv=0).
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
[Do not use get_enable_apicv; consider irqchip_split in svm.c. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -873,6 +873,8 @@ enum kvm_irqchip_mode {
 	KVM_IRQCHIP_SPLIT,        /* created with KVM_CAP_SPLIT_IRQCHIP */
 };
 
+#define APICV_INHIBIT_REASON_DISABLE    0
+
 struct kvm_arch {
 	unsigned long n_used_mmu_pages;
 	unsigned long n_requested_mmu_pages;
@@ -904,6 +906,7 @@ struct kvm_arch {
 	struct kvm_apic_map *apic_map;
 
 	bool apic_access_page_done;
+	unsigned long apicv_inhibit_reasons;
 
 	gpa_t wall_clock;
 
@@ -1478,6 +1481,8 @@ gpa_t kvm_mmu_gva_to_gpa_system(struct kvm_vcpu *vcpu, gva_t gva,
 				struct x86_exception *exception);
 
 void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu);
+bool kvm_apicv_activated(struct kvm *kvm);
+void kvm_apicv_init(struct kvm *kvm, bool enable);
 
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
 

arch/x86/kvm/svm.c

@@ -2052,6 +2052,18 @@ static int avic_vm_init(struct kvm *kvm)
 	return err;
 }
 
+static int svm_vm_init(struct kvm *kvm)
+{
+	if (avic) {
+		int ret = avic_vm_init(kvm);
+		if (ret)
+			return ret;
+	}
+
+	kvm_apicv_init(kvm, avic && irqchip_split(kvm));
+	return 0;
+}
+
 static inline int
 avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu, bool r)
 {
@@ -7274,7 +7286,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 
 	.vm_alloc = svm_vm_alloc,
 	.vm_free = svm_vm_free,
-	.vm_init = avic_vm_init,
+	.vm_init = svm_vm_init,
 	.vm_destroy = svm_vm_destroy,
 
 	.prepare_guest_switch = svm_prepare_guest_switch,

arch/x86/kvm/vmx/vmx.c

@@ -6813,6 +6813,7 @@ static int vmx_vm_init(struct kvm *kvm)
 			break;
 		}
 	}
+	kvm_apicv_init(kvm, enable_apicv);
 	return 0;
 }
 

arch/x86/kvm/x86.c

@@ -7469,6 +7469,23 @@ void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu)
 	kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu);
 }
 
+bool kvm_apicv_activated(struct kvm *kvm)
+{
+	return (READ_ONCE(kvm->arch.apicv_inhibit_reasons) == 0);
+}
+EXPORT_SYMBOL_GPL(kvm_apicv_activated);
+
+void kvm_apicv_init(struct kvm *kvm, bool enable)
+{
+	if (enable)
+		clear_bit(APICV_INHIBIT_REASON_DISABLE,
+			  &kvm->arch.apicv_inhibit_reasons);
+	else
+		set_bit(APICV_INHIBIT_REASON_DISABLE,
+			&kvm->arch.apicv_inhibit_reasons);
+}
+EXPORT_SYMBOL_GPL(kvm_apicv_init);
+
 static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)
 {
 	struct kvm_vcpu *target = NULL;
@@ -9219,10 +9236,11 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 		return r;
 
 	if (irqchip_in_kernel(vcpu->kvm)) {
-		vcpu->arch.apicv_active = kvm_x86_ops->get_enable_apicv(vcpu->kvm);
 		r = kvm_create_lapic(vcpu, lapic_timer_advance_ns);
 		if (r < 0)
 			goto fail_mmu_destroy;
+		if (kvm_apicv_activated(vcpu->kvm))
+			vcpu->arch.apicv_active = true;
 	} else
 		static_key_slow_inc(&kvm_no_apic_vcpu);