Messages in this thread | | | Date | Mon, 19 Jun 2023 12:02:19 -0500 | Subject | Re: [patch v3 2/7] x86/smp: Dont access non-existing CPUID leaf | From | "Limonciello, Mario" <> |
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On 6/15/2023 3:33 PM, Thomas Gleixner wrote: > From: Tony Battersby <tonyb@cybernetics.com> > > stop_this_cpu() tests CPUID leaf 0x8000001f::EAX unconditionally. CPUs > return the content of the highest supported leaf when a non-existing leaf > is read. So the result of the test is lottery except on AMD CPUs which > support that leaf. > > 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")
Thanks for this fix. This particular patch should probably also CC to stable.
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> Signed-off-by: Tony Battersby <tonyb@cybernetics.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Link: https://lore.kernel.org/r/3817d810-e0f1-8ef8-0bbd-663b919ca49b@cybernetics.com > --- > 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(); > > /* >
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