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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) <bp@alien8.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Srikanth Aithal <sraithal@amd.com> Link: https://lore.kernel.org/r/20240327154317.29909-3-bp@alien8.de
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@ -150,8 +150,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
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extern void setup_clear_cpu_cap(unsigned int bit);
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extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
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#define setup_force_cpu_cap(bit) do { \
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set_cpu_cap(&boot_cpu_data, bit); \
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#define setup_force_cpu_cap(bit) do { \
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\
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if (!boot_cpu_has(bit)) \
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WARN_ON(alternatives_patched); \
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\
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set_cpu_cap(&boot_cpu_data, bit); \
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set_bit(bit, (unsigned long *)cpu_caps_set); \
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} while (0)
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@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
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if (WARN_ON(feature >= MAX_FEATURE_BITS))
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return;
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if (boot_cpu_has(feature))
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WARN_ON(alternatives_patched);
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clear_feature(c, feature);
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/* Collect all features to disable, handling dependencies */
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