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

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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: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2023-07-21 13:18:43 -07:00
parent 5e408396c6
commit 119b5cb4ff
3 changed files with 14 additions and 33 deletions
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29
arch/x86/kernel/reboot.c
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@@ -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;
cpu_emergency_vmxoff();
rcu_read_lock();
callback = rcu_dereference(cpu_emergency_virt_callback);
if (callback)
callback();
rcu_read_unlock();
/* KVM_AMD doesn't yet utilize the common callback. */
cpu_emergency_svm_disable();
}