KVM: x86: Force kvm_rebooting=true during emergency reboot/crash

Set kvm_rebooting when virtualization is disabled in an emergency so that
KVM eats faults on virtualization instructions even if kvm_reboot() isn't
reached.

Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-18-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/svm/svm.c

@@ -605,6 +605,8 @@ static inline void kvm_cpu_svm_disable(void)
 
 static void svm_emergency_disable(void)
 {
+	kvm_rebooting = true;
+
 	kvm_cpu_svm_disable();
 }
 

arch/x86/kvm/vmx/vmx.c

@@ -752,6 +752,8 @@ static void vmx_emergency_disable(void)
 	int cpu = raw_smp_processor_id();
 	struct loaded_vmcs *v;
 
+	kvm_rebooting = true;
+
 	list_for_each_entry(v, &per_cpu(loaded_vmcss_on_cpu, cpu),
 			    loaded_vmcss_on_cpu_link)
 		vmcs_clear(v->vmcs);