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

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Message-ID: <20221130233650.1404148-5-seanjc@google.com>
Date:   Wed, 30 Nov 2022 23:36:50 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Tom Lendacky <thomas.lendacky@....com>, stable@...r.kernel
Subject: [PATCH v4 4/4] 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: fba4f472b33a ("x86/reboot: Turn off KVM when halting a CPU")
Cc: stable@...r.kernel
Signed-off-by: Sean Christopherson <seanjc@...gle.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