Attempt to disable virtualization during an emergency reboot if and only
if there is a registered virt callback, i.e. iff a hypervisor (KVM) is
active. If there's no active hypervisor, then the CPU can't be operating
with VMX or SVM enabled (barring an egregious bug).
Checking for a valid callback instead of simply for SVM or VMX support
can also eliminates spurious NMIs by avoiding the unecessary call to
nmi_shootdown_cpus_on_restart().
Note, IRQs are disabled, which prevents KVM from coming along and
enabling virtualization after the fact.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kernel/reboot.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 85cb2dfcb67b..98e5db3fd7f4 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -22,7 +22,6 @@
#include <asm/reboot_fixups.h>
#include <asm/reboot.h>
#include <asm/pci_x86.h>
-#include <asm/virtext.h>
#include <asm/cpu.h>
#include <asm/nmi.h>
#include <asm/smp.h>
@@ -589,7 +588,7 @@ static void emergency_reboot_disable_virtualization(void)
* Do the NMI shootdown even if virtualization is off on _this_ CPU, as
* other CPUs may have virtualization enabled.
*/
- if (cpu_has_vmx() || cpu_has_svm(NULL)) {
+ if (rcu_access_pointer(cpu_emergency_virt_callback)) {
/* Safely force _this_ CPU out of VMX/SVM operation. */
cpu_emergency_disable_virtualization();
--
2.41.0.487.g6d72f3e995-goog
