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x86/asm: Cleanup prefetch primitives

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This is based on a patch originally by hpa.

With the current improvements to the alternatives, we can simply use %P1
as a mem8 operand constraint and rely on the toolchain to generate the
proper instruction sizes. For example, on 32-bit, where we use an empty
old instruction we get:

  apply_alternatives: feat: 6*32+8, old: (c104648b, len: 4), repl: (c195566c, len: 4)
  c104648b: alt_insn: 90 90 90 90
  c195566c: rpl_insn: 0f 0d 4b 5c

  ...

  apply_alternatives: feat: 6*32+8, old: (c18e09b4, len: 3), repl: (c1955948, len: 3)
  c18e09b4: alt_insn: 90 90 90
  c1955948: rpl_insn: 0f 0d 08

  ...

  apply_alternatives: feat: 6*32+8, old: (c1190cf9, len: 7), repl: (c1955a79, len: 7)
  c1190cf9: alt_insn: 90 90 90 90 90 90 90
  c1955a79: rpl_insn: 0f 0d 0d a0 d4 85 c1

all with the proper padding done depending on the size of the
replacement instruction the compiler generates.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Borislav Petkov
2015-01-18 17:48:18 +01:00
parent c70e1b475f
commit a930dc4543
3 changed files with 13 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/include/asm/processor.h
View File

@@ -761,10 +761,10 @@ extern char ignore_fpu_irq;
#define ARCH_HAS_SPINLOCK_PREFETCH
#ifdef CONFIG_X86_32
# define BASE_PREFETCH ASM_NOP4
# define BASE_PREFETCH ""
# define ARCH_HAS_PREFETCH
#else
# define BASE_PREFETCH "prefetcht0 (%1)"
# define BASE_PREFETCH "prefetcht0 %P1"
#endif
/*
@@ -775,10 +775,9 @@ extern char ignore_fpu_irq;
*/
static inline void prefetch(const void *x)
{
alternative_input(BASE_PREFETCH,
"prefetchnta (%1)",
alternative_input(BASE_PREFETCH, "prefetchnta %P1",
X86_FEATURE_XMM,
"r" (x));
"m" (*(const char *)x));
}
/*
@@ -788,10 +787,9 @@ static inline void prefetch(const void *x)
*/
static inline void prefetchw(const void *x)
{
alternative_input(BASE_PREFETCH,
"prefetchw (%1)",
X86_FEATURE_3DNOW,
"r" (x));
alternative_input(BASE_PREFETCH, "prefetchw %P1",
X86_FEATURE_3DNOWPREFETCH,
"m" (*(const char *)x));
}
static inline void spin_lock_prefetch(const void *x)