From f7df17d128075bf1c50e87e0c0721bb0012d086b Mon Sep 17 00:00:00 2001 From: Tony Battersby Date: Thu, 15 Jun 2023 22:33:52 +0200 Subject: [PATCH] x86/smp: Dont access non-existing CPUID leaf 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 Signed-off-by: Thomas Gleixner Reviewed-by: Mario Limonciello Reviewed-by: Borislav Petkov (AMD) 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 Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/process.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index cb8024017f25e..2fed8aafb5214 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -756,6 +756,7 @@ 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(); @@ -770,7 +771,7 @@ 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 @@ -784,7 +785,7 @@ 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(); /* -- 2.47.2