kvm: x86: Introduce x86 ops hook for pre-update APICv

AMD SVM AVIC needs to update APIC backing page mapping before changing
APICv mode. Introduce struct kvm_x86_ops.pre_update_apicv_exec_ctrl
function hook to be called prior KVM APICv update request to each vcpu.
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1124,6 +1124,7 @@ struct kvm_x86_ops {
 	void (*enable_irq_window)(struct kvm_vcpu *vcpu);
 	void (*update_cr8_intercept)(struct kvm_vcpu *vcpu, int tpr, int irr);
 	bool (*check_apicv_inhibit_reasons)(ulong bit);
+	void (*pre_update_apicv_exec_ctrl)(struct kvm *kvm, bool activate);
 	void (*refresh_apicv_exec_ctrl)(struct kvm_vcpu *vcpu);
 	void (*hwapic_irr_update)(struct kvm_vcpu *vcpu, int max_irr);
 	void (*hwapic_isr_update)(struct kvm_vcpu *vcpu, int isr);

arch/x86/kvm/svm.c

@@ -7305,6 +7305,11 @@ static bool svm_check_apicv_inhibit_reasons(ulong bit)
 	return supported & BIT(bit);
 }
 
+static void svm_pre_update_apicv_exec_ctrl(struct kvm *kvm, bool activate)
+{
+	avic_update_access_page(kvm, activate);
+}
+
 static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.cpu_has_kvm_support = has_svm,
 	.disabled_by_bios = is_disabled,
@@ -7381,6 +7386,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.set_virtual_apic_mode = svm_set_virtual_apic_mode,
 	.refresh_apicv_exec_ctrl = svm_refresh_apicv_exec_ctrl,
 	.check_apicv_inhibit_reasons = svm_check_apicv_inhibit_reasons,
+	.pre_update_apicv_exec_ctrl = svm_pre_update_apicv_exec_ctrl,
 	.load_eoi_exitmap = svm_load_eoi_exitmap,
 	.hwapic_irr_update = svm_hwapic_irr_update,
 	.hwapic_isr_update = svm_hwapic_isr_update,

arch/x86/kvm/x86.c

@@ -8049,6 +8049,8 @@ void kvm_request_apicv_update(struct kvm *kvm, bool activate, ulong bit)
 	}
 
 	trace_kvm_apicv_update_request(activate, bit);
+	if (kvm_x86_ops->pre_update_apicv_exec_ctrl)
+		kvm_x86_ops->pre_update_apicv_exec_ctrl(kvm, activate);
 	kvm_make_all_cpus_request(kvm, KVM_REQ_APICV_UPDATE);
 }
 EXPORT_SYMBOL_GPL(kvm_request_apicv_update);