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x86/alternatives, x86/fpu: Add 'alternatives_patched' debug flag and use it in xsave_state() 

We'd like to use xsave_state() earlier, but its SYSTEM_BOOTING check
is too imprecise.

The real condition that xsave_state() would like to check is whether
alternative XSAVE instructions were patched into the kernel image
already.

Add such a (read-mostly) debug flag and use it in xsave_state().

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Ingo Molnar 2015-04-30 09:09:26 +02:00
parent 2e85591a6c
commit 5e907bb045
3 changed files with 12 additions and 1 deletions
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6
arch/x86/include/asm/alternative.h
View File

@ -52,6 +52,12 @@ struct alt_instr {
u8 padlen; /* length of build-time padding */
} __packed;
/*
* Debug flag that can be tested to see whether alternative
* instructions were patched in already:
*/
extern int alternatives_patched;
extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);

2
arch/x86/include/asm/fpu/xstate.h
View File

@ -119,7 +119,7 @@ static inline int xsave_state(struct xsave_struct *fx)
u32 hmask = mask >> 32;
int err = 0;
WARN_ON(system_state == SYSTEM_BOOTING);
WARN_ON(!alternatives_patched);
/*
* If xsaves is enabled, xsaves replaces xsaveopt because

5
arch/x86/kernel/alternative.c
View File

@ -21,6 +21,10 @@
#include <asm/io.h>
#include <asm/fixmap.h>
int __read_mostly alternatives_patched;
EXPORT_SYMBOL_GPL(alternatives_patched);
#define MAX_PATCH_LEN (255-1)
static int __initdata_or_module debug_alternative;
@ -627,6 +631,7 @@ void __init alternative_instructions(void)
apply_paravirt(__parainstructions, __parainstructions_end);
restart_nmi();
alternatives_patched = 1;
}
/**