[PATCH v4 4/4] x86/reboot: Disable SVM, not just VMX, when stopping CPUs

Sean Christopherson
2022-11-30T23:37:16Z

Disable SVM and more importantly force GIF=1 when halting a CPU or
rebooting the machine. Similar to VMX, SVM allows software to block
INITs via CLGI, and thus can be problematic for a crash/reboot. The
window for failure is smaller with SVM as INIT is only blocked while
GIF=0, i.e. between CLGI and STGI, but the window does exist.

Fixes: fba4f472b33a ("x86/reboot: Turn off KVM when halting a CPU")
Cc: stable@vger.kernel
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kernel/smp.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 06db901fabe8..375b33ecafa2 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -32,7 +32,7 @@
#include <asm/mce.h>
#include <asm/trace/irq_vectors.h>
#include <asm/kexec.h>
-#include <asm/virtext.h>
+#include <asm/reboot.h>

/*
* Some notes on x86 processor bugs affecting SMP operation:
@@ -122,7 +122,7 @@ static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
return NMI_HANDLED;

- cpu_emergency_vmxoff();
+ cpu_emergency_disable_virtualization();
stop_this_cpu(NULL);

return NMI_HANDLED;
@@ -134,7 +134,7 @@ static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
DEFINE_IDTENTRY_SYSVEC(sysvec_reboot)
{
ack_APIC_irq();
- cpu_emergency_vmxoff();
+ cpu_emergency_disable_virtualization();
stop_this_cpu(NULL);
}

--
2.38.1.584.g0f3c55d4c2-goog