@@ -538,31 +538,21 @@ static void emergency_vmx_disable_all(void)
local_irq_disable();
/*
- * We need to disable VMX on all CPUs before rebooting, otherwise
- * we risk hanging up the machine, because the CPU ignores INIT
- * signals when VMX is enabled.
+ * Disable VMX on all CPUs before rebooting, otherwise we risk hanging
+ * the machine, because the CPU blocks INIT when it's in VMX root.
*
- * We can't take any locks and we may be on an inconsistent
- * state, so we use NMIs as IPIs to tell the other CPUs to disable
- * VMX and halt.
+ * We can't take any locks and we may be on an inconsistent state, so
+ * use NMIs as IPIs to tell the other CPUs to exit VMX root and halt.
*
- * For safety, we will avoid running the nmi_shootdown_cpus()
- * stuff unnecessarily, but we don't have a way to check
- * if other CPUs have VMX enabled. So we will call it only if the
- * CPU we are running on has VMX enabled.
- *
- * We will miss cases where VMX is not enabled on all CPUs. This
- * shouldn't do much harm because KVM always enable VMX on all
- * CPUs anyway. But we can miss it on the small window where KVM
- * is still enabling VMX.
+ * Do the NMI shootdown even if VMX if off on _this_ CPU, as that
+ * doesn't prevent a different CPU from being in VMX root operation.
*/
- if (cpu_has_vmx() && cpu_vmx_enabled()) {
- /* Disable VMX on this CPU. */
- cpu_vmxoff();
+ if (cpu_has_vmx()) {
+ /* Safely force _this_ CPU out of VMX root operation. */
+ __cpu_emergency_vmxoff();
- /* Halt and disable VMX on the other CPUs */
+ /* Halt and exit VMX root operation on the other CPUs. */
nmi_shootdown_cpus(vmxoff_nmi);
-
}
}
Force all CPUs to do VMXOFF (via NMI shootdown) during an emergency reboot if VMX is _supported_, as VMX being off on the current CPU does not prevent other CPUs from being in VMX root (post-VMXON). This fixes a bug where a crash/panic reboot could leave other CPUs in VMX root and prevent them from being woken via INIT-SIPI-SIPI in the new kernel. Fixes: d176720d34c7 ("x86: disable VMX on all CPUs on reboot") Cc: stable@vger.kernel.org Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: David P. Reed <dpreed@deepplum.com> [sean: reworked changelog and further tweaked comment] Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kernel/reboot.c | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-)