Commit 119b5cb4 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

x86/reboot: KVM: Handle VMXOFF in KVM's reboot callback 



Use KVM VMX's reboot/crash callback to do VMXOFF in an emergency instead
of manually and blindly doing VMXOFF.  There's no need to attempt VMXOFF
if a hypervisor, i.e. KVM, isn't loaded/active, i.e. if the CPU can't
possibly be post-VMXON.

Reviewed-by: default avatarKai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-4-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 5e408396

arch/x86/include/asm/virtext.h

+0 −10
Original line number Diff line number Diff line
@@ -70,16 +70,6 @@ static inline void __cpu_emergency_vmxoff(void) 
		cpu_vmxoff();

}



/** Disable VMX if it is supported and enabled on the current CPU

 */

static inline void cpu_emergency_vmxoff(void)

{

	if (cpu_has_vmx())

		__cpu_emergency_vmxoff();

}









/*

 * SVM functions:

arch/x86/kernel/reboot.c

+9 −20
Original line number Diff line number Diff line
@@ -787,13 +787,7 @@ void machine_crash_shutdown(struct pt_regs *regs) 
}

#endif



/*

 * This is used to VMCLEAR all VMCSs loaded on the

 * processor. And when loading kvm_intel module, the

 * callback function pointer will be assigned.

 *

 * protected by rcu.

 */

/* RCU-protected callback to disable virtualization prior to reboot. */

static cpu_emergency_virt_cb __rcu *cpu_emergency_virt_callback;



void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback)
@@ -815,17 +809,6 @@ void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback) 
}

EXPORT_SYMBOL_GPL(cpu_emergency_unregister_virt_callback);



static inline void cpu_crash_vmclear_loaded_vmcss(void)

{

	cpu_emergency_virt_cb *callback;



	rcu_read_lock();

	callback = rcu_dereference(cpu_emergency_virt_callback);

	if (callback)

		callback();

	rcu_read_unlock();

}



/* This is the CPU performing the emergency shutdown work. */

int crashing_cpu = -1;
@@ -836,9 +819,15 @@ int crashing_cpu = -1; 
 */

void cpu_emergency_disable_virtualization(void)

{

	cpu_crash_vmclear_loaded_vmcss();

	cpu_emergency_virt_cb *callback;



	rcu_read_lock();

	callback = rcu_dereference(cpu_emergency_virt_callback);

	if (callback)

		callback();

	rcu_read_unlock();



	cpu_emergency_vmxoff();

	/* KVM_AMD doesn't yet utilize the common callback. */

	cpu_emergency_svm_disable();

}

arch/x86/kvm/vmx/vmx.c

+5 −3
Original line number Diff line number Diff line
@@ -725,7 +725,7 @@ static int vmx_set_guest_uret_msr(struct vcpu_vmx *vmx, 
	return ret;

}



static void crash_vmclear_local_loaded_vmcss(void)

static void vmx_emergency_disable(void)

{

	int cpu = raw_smp_processor_id();

	struct loaded_vmcs *v;
@@ -733,6 +733,8 @@ static void crash_vmclear_local_loaded_vmcss(void) 
	list_for_each_entry(v, &per_cpu(loaded_vmcss_on_cpu, cpu),

			    loaded_vmcss_on_cpu_link)

		vmcs_clear(v->vmcs);



	__cpu_emergency_vmxoff();

}



static void __loaded_vmcs_clear(void *arg)
@@ -8571,7 +8573,7 @@ static void __vmx_exit(void) 
{

	allow_smaller_maxphyaddr = false;



	cpu_emergency_unregister_virt_callback(crash_vmclear_local_loaded_vmcss);

	cpu_emergency_unregister_virt_callback(vmx_emergency_disable);



	vmx_cleanup_l1d_flush();

}
@@ -8619,7 +8621,7 @@ static int __init vmx_init(void) 
		pi_init_cpu(cpu);

	}



	cpu_emergency_register_virt_callback(crash_vmclear_local_loaded_vmcss);

	cpu_emergency_register_virt_callback(vmx_emergency_disable);



	vmx_check_vmcs12_offsets();