[PATCH v2 4/6] KVM: Add arch hooks for enabling/disabling virtualization

[Sean Christopherson <seanjc@google.com>]

Add arch hooks that are invoked when KVM enables/disable virtualization.
x86 will use the hooks to register an "emergency disable" callback, which
is essentially an x86-specific shutdown notifier that is used when the
kernel is doing an emergency reboot/shutdown/kexec.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 include/linux/kvm_host.h |  2 ++
 virt/kvm/kvm_main.c      | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7b57878c8c18..701b16290932 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1514,6 +1514,8 @@ static inline void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {}
 #endif
 
 #ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
+void kvm_arch_enable_virtualization(void);
+void kvm_arch_disable_virtualization(void);
 int kvm_arch_hardware_enable(void);
 void kvm_arch_hardware_disable(void);
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8d331ab3aef7..16adeb6b5bef 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5505,6 +5505,16 @@ static DEFINE_PER_CPU(bool, hardware_enabled);
 static DEFINE_MUTEX(kvm_usage_lock);
 static int kvm_usage_count;
 
+__weak void kvm_arch_enable_virtualization(void)
+{
+
+}
+
+__weak void kvm_arch_disable_virtualization(void)
+{
+
+}
+
 static int __kvm_enable_virtualization(void)
 {
 	if (__this_cpu_read(hardware_enabled))
@@ -5604,6 +5614,8 @@ static int kvm_enable_virtualization(void)
 	if (kvm_usage_count++)
 		return 0;
 
+	kvm_arch_enable_virtualization();
+
 	r = cpuhp_setup_state(CPUHP_AP_KVM_ONLINE, "kvm/cpu:online",
 			      kvm_online_cpu, kvm_offline_cpu);
 	if (r)
@@ -5634,6 +5646,7 @@ static int kvm_enable_virtualization(void)
 	unregister_syscore_ops(&kvm_syscore_ops);
 	cpuhp_remove_state(CPUHP_AP_KVM_ONLINE);
 err_cpuhp:
+	kvm_arch_disable_virtualization();
 	--kvm_usage_count;
 	return r;
 }
@@ -5647,6 +5660,7 @@ static void kvm_disable_virtualization(void)
 
 	unregister_syscore_ops(&kvm_syscore_ops);
 	cpuhp_remove_state(CPUHP_AP_KVM_ONLINE);
+	kvm_arch_disable_virtualization();
 }
 
 static int kvm_init_virtualization(void)
-- 
2.45.0.215.g3402c0e53f-goog