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Merge branch 'x86-alternatives-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 alternative instruction updates from Ingo Molnar:
 "Small RDTSCP opimization, enabled by the newly added ALTERNATIVE_3(),
  and other small improvements"

* 'x86-alternatives-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/TSC: Use RDTSCP
  x86/alternatives: Add an ALTERNATIVE_3() macro
  x86/alternatives: Print containing function
  x86/alternatives: Add macro comments
This commit is contained in:
Linus Torvalds 2019-03-06 08:45:46 -08:00
commit 6ea98b4baa
3 changed files with 49 additions and 12 deletions
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41
arch/x86/include/asm/alternative.h
View File

@ -94,13 +94,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
#define alt_total_slen alt_end_marker"b-661b"
#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
#define __OLDINSTR(oldinstr, num) \
"661:\n\t" oldinstr "\n662:\n" \
".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"
#define OLDINSTR(oldinstr, num) \
__OLDINSTR(oldinstr, num) \
"# ALT: oldnstr\n" \
"661:\n\t" oldinstr "\n662:\n" \
"# ALT: padding\n" \
".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
alt_end_marker ":\n"
/*
@ -116,11 +115,23 @@ static inline int alternatives_text_reserved(void *start, void *end)
* additionally longer than the first replacement alternative.
*/
#define OLDINSTR_2(oldinstr, num1, num2) \
"# ALT: oldinstr2\n" \
"661:\n\t" oldinstr "\n662:\n" \
"# ALT: padding2\n" \
".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
alt_end_marker ":\n"
#define OLDINSTR_3(oldinsn, n1, n2, n3) \
"# ALT: oldinstr3\n" \
"661:\n\t" oldinsn "\n662:\n" \
"# ALT: padding3\n" \
".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
" - (" alt_slen ")) > 0) * " \
"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
" - (" alt_slen ")), 0x90\n" \
alt_end_marker ":\n"
#define ALTINSTR_ENTRY(feature, num) \
" .long 661b - .\n" /* label */ \
" .long " b_replacement(num)"f - .\n" /* new instruction */ \
@ -129,8 +140,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
" .byte " alt_rlen(num) "\n" /* replacement len */ \
" .byte " alt_pad_len "\n" /* pad len */
#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
"# ALT: replacement " #num "\n" \
b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, feature) \
@ -153,6 +165,19 @@ static inline int alternatives_text_reserved(void *start, void *end)
ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
".popsection\n"
#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
OLDINSTR_3(oldinsn, 1, 2, 3) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(feat1, 1) \
ALTINSTR_ENTRY(feat2, 2) \
ALTINSTR_ENTRY(feat3, 3) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinsn1, feat1, 1) \
ALTINSTR_REPLACEMENT(newinsn2, feat2, 2) \
ALTINSTR_REPLACEMENT(newinsn3, feat3, 3) \
".popsection\n"
/*
* Alternative instructions for different CPU types or capabilities.
*

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

@ -217,6 +217,8 @@ static __always_inline unsigned long long rdtsc(void)
*/
static __always_inline unsigned long long rdtsc_ordered(void)
{
DECLARE_ARGS(val, low, high);
/*
* The RDTSC instruction is not ordered relative to memory
* access. The Intel SDM and the AMD APM are both vague on this
@ -227,9 +229,19 @@ static __always_inline unsigned long long rdtsc_ordered(void)
* ordering guarantees as reading from a global memory location
* that some other imaginary CPU is updating continuously with a
* time stamp.
*
* Thus, use the preferred barrier on the respective CPU, aiming for
* RDTSCP as the default.
*/
barrier_nospec();
return rdtsc();
asm volatile(ALTERNATIVE_3("rdtsc",
"mfence; rdtsc", X86_FEATURE_MFENCE_RDTSC,
"lfence; rdtsc", X86_FEATURE_LFENCE_RDTSC,
"rdtscp", X86_FEATURE_RDTSCP)
: EAX_EDX_RET(val, low, high)
/* RDTSCP clobbers ECX with MSR_TSC_AUX. */
:: "ecx");
return EAX_EDX_VAL(val, low, high);
}
static inline unsigned long long native_read_pmc(int counter)

4
arch/x86/kernel/alternative.c
View File

@ -394,10 +394,10 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
continue;
}
DPRINTK("feat: %d*32+%d, old: (%px len: %d), repl: (%px, len: %d), pad: %d",
DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
a->cpuid >> 5,
a->cpuid & 0x1f,
instr, a->instrlen,
instr, instr, a->instrlen,
replacement, a->replacementlen, a->padlen);
DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr);