This is a note to let you know that I've just added the patch titled
x86/smp: Dont access non-existing CPUID leaf
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-smp-dont-access-non-existing-cpuid-leaf.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 9b040453d4440659f33dc6f0aa26af418ebfe70b Mon Sep 17 00:00:00 2001
From: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Date: Thu, 15 Jun 2023 22:33:52 +0200
Subject: x86/smp: Dont access non-existing CPUID leaf
From: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
commit 9b040453d4440659f33dc6f0aa26af418ebfe70b upstream.
stop_this_cpu() tests CPUID leaf 0x8000001f::EAX unconditionally. Intel
CPUs return the content of the highest supported leaf when a non-existing
leaf is read, while AMD CPUs return all zeros for unsupported leafs.
So the result of the test on Intel CPUs is lottery.
While harmless it's incorrect and causes the conditional wbinvd() to be
issued where not required.
Check whether the leaf is supported before reading it.
[ tglx: Adjusted changelog ]
Fixes: 08f253ec3767 ("x86/cpu: Clear SME feature flag when not in use")
Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/3817d810-e0f1-8ef8-0bbd-663b919ca49b@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20230615193330.322186388@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/process.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -763,6 +763,7 @@ struct cpumask cpus_stop_mask;
void __noreturn stop_this_cpu(void *dummy)
{
+ struct cpuinfo_x86 *c = this_cpu_ptr(&cpu_info);
unsigned int cpu = smp_processor_id();
local_irq_disable();
@@ -777,7 +778,7 @@ void __noreturn stop_this_cpu(void *dumm
*/
set_cpu_online(cpu, false);
disable_local_APIC();
- mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
+ mcheck_cpu_clear(c);
/*
* Use wbinvd on processors that support SME. This provides support
@@ -791,7 +792,7 @@ void __noreturn stop_this_cpu(void *dumm
* Test the CPUID bit directly because the machine might've cleared
* X86_FEATURE_SME due to cmdline options.
*/
- if (cpuid_eax(0x8000001f) & BIT(0))
+ if (c->extended_cpuid_level >= 0x8000001f && (cpuid_eax(0x8000001f) & BIT(0)))
native_wbinvd();
/*
Patches currently in stable-queue which might be from tonyb@xxxxxxxxxxxxxxx are
queue-6.4/x86-smp-dont-access-non-existing-cpuid-leaf.patch
queue-6.4/x86-smp-make-stop_other_cpus-more-robust.patch
