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x86/smp: Dont access non-existing CPUID leaf 

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: 08f253ec37 ("x86/cpu: Clear SME feature flag when not in use")
Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/3817d810-e0f1-8ef8-0bbd-663b919ca49b@cybernetics.com
Link: https://lore.kernel.org/r/20230615193330.322186388@linutronix.de
This commit is contained in:
Tony Battersby 2023-06-15 22:33:52 +02:00 committed by Thomas Gleixner
parent 1f5e7eb786
commit 9b040453d4
1 changed files with 3 additions and 2 deletions
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5
arch/x86/kernel/process.c
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@ -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 *dummy)
*/
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 *dummy)
* 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();
/*