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x86/cpuid: Add generic table for CPUID dependencies

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Some CPUID features depend on other features. Currently it's
possible to to clear dependent features, but not clear the base features,
which can cause various interesting problems.

This patch implements a generic table to describe dependencies
between CPUID features, to be used by all code that clears
CPUID.

Some subsystems (like XSAVE) had an own implementation of this,
but it's better to do it all in a single place for everyone.

Then clear_cpu_cap and setup_clear_cpu_cap always look up
this table and clear all dependencies too.

This is intended to be a practical table: only for features
that make sense to clear. If someone for example clears FPU,
or other features that are essentially part of the required
base feature set, not much is going to work. Handling
that is right now out of scope. We're only handling
features which can be usefully cleared.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jonathan McDowell <noodles@earth.li>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171013215645.23166-3-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andi Kleen
2017-10-13 14:56:42 -07:00
committed by Ingo Molnar
parent cbe9637502
commit 0b00de857a
4 changed files with 123 additions and 5 deletions
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9
arch/x86/include/asm/cpufeature.h
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@@ -125,11 +125,10 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
#define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit)
#define set_cpu_cap(c, bit) set_bit(bit, (unsigned long *)((c)->x86_capability))
#define clear_cpu_cap(c, bit) clear_bit(bit, (unsigned long *)((c)->x86_capability))
#define setup_clear_cpu_cap(bit) do { \
clear_cpu_cap(&boot_cpu_data, bit); \
set_bit(bit, (unsigned long *)cpu_caps_cleared); \
} while (0)
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); \
set_bit(bit, (unsigned long *)cpu_caps_set); \