From: Borislav Petkov (AMD) Date: Wed, 27 Mar 2024 15:43:14 +0000 (+0100) Subject: x86/alternatives: Catch late X86_FEATURE modifiers X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=ee8962082a4413dba1a1b3d3d23490c5221f3b8a;p=linux.git x86/alternatives: Catch late X86_FEATURE modifiers After alternatives have been patched, changes to the X86_FEATURE flags won't take effect and could potentially even be wrong. Warn about it. This is something which has been long overdue. Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Ingo Molnar Tested-by: Srikanth Aithal Link: https://lore.kernel.org/r/20240327154317.29909-3-bp@alien8.de --- diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 686e92d2663ee..f07687ddb13d8 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -150,8 +150,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; extern void setup_clear_cpu_cap(unsigned int bit); extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit); -#define setup_force_cpu_cap(bit) do { \ - set_cpu_cap(&boot_cpu_data, bit); \ +#define setup_force_cpu_cap(bit) do { \ + \ + if (!boot_cpu_has(bit)) \ + WARN_ON(alternatives_patched); \ + \ + set_cpu_cap(&boot_cpu_data, bit); \ set_bit(bit, (unsigned long *)cpu_caps_set); \ } while (0) diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c index b7174209d855c..5dd427c6feb2e 100644 --- a/arch/x86/kernel/cpu/cpuid-deps.c +++ b/arch/x86/kernel/cpu/cpuid-deps.c @@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature) if (WARN_ON(feature >= MAX_FEATURE_BITS)) return; + if (boot_cpu_has(feature)) + WARN_ON(alternatives_patched); + clear_feature(c, feature); /* Collect all features to disable, handling dependencies */