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x86/reboot: Disable SVM, not just VMX, when stopping CPUs 

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: fba4f472b3 ("x86/reboot: Turn off KVM when halting a CPU")
Cc: stable@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20221130233650.1404148-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2022-11-30 23:36:50 +00:00
parent d81f952aa6
commit a2b07fa7b9
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kernel/smp.c
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@ -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);
}