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x86-64: Reduce SMP locks table size

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Reduce the SMP locks table size by using relative pointers instead of
absolute ones, thus cutting the table size by half.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <4BCF30FE020000780003B3B6@vpn.id2.novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Jan Beulich 2010-04-21 16:08:14 +01:00 committed by H. Peter Anvin
parent 402af0d7c6
commit 5967ed87ad
3 changed files with 29 additions and 24 deletions
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4
arch/x86/include/asm/alternative-asm.h
View File

@ -6,8 +6,8 @@
.macro LOCK_PREFIX .macro LOCK_PREFIX
1: lock 1: lock
.section .smp_locks,"a" .section .smp_locks,"a"
_ASM_ALIGN .balign 4
_ASM_PTR 1b .long 1b - .
.previous .previous
.endm .endm
#else #else

4
arch/x86/include/asm/alternative.h
View File

@ -30,8 +30,8 @@
#ifdef CONFIG_SMP #ifdef CONFIG_SMP
#define LOCK_PREFIX \ #define LOCK_PREFIX \
".section .smp_locks,\"a\"\n" \ ".section .smp_locks,\"a\"\n" \
_ASM_ALIGN "\n" \ ".balign 4\n" \
_ASM_PTR "661f\n" /* address */ \ ".long 661f - .\n" /* offset */ \
".previous\n" \ ".previous\n" \
"661:\n\tlock; " "661:\n\tlock; "

45
arch/x86/kernel/alternative.c
View File

@ -194,7 +194,7 @@ static void __init_or_module add_nops(void *insns, unsigned int len)
} }
extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
extern u8 *__smp_locks[], *__smp_locks_end[]; extern s32 __smp_locks[], __smp_locks_end[];
static void *text_poke_early(void *addr, const void *opcode, size_t len); static void *text_poke_early(void *addr, const void *opcode, size_t len);
/* Replace instructions with better alternatives for this CPU type. /* Replace instructions with better alternatives for this CPU type.
@ -235,37 +235,39 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
#ifdef CONFIG_SMP #ifdef CONFIG_SMP
static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) static void alternatives_smp_lock(const s32 *start, const s32 *end,
u8 *text, u8 *text_end)
{ {
u8 **ptr; const s32 *poff;
mutex_lock(&text_mutex); mutex_lock(&text_mutex);
for (ptr = start; ptr < end; ptr++) { for (poff = start; poff < end; poff++) {
if (*ptr < text) u8 *ptr = (u8 *)poff + *poff;
continue;
if (*ptr > text_end) if (!*poff || ptr < text || ptr >= text_end)
continue; continue;
/* turn DS segment override prefix into lock prefix */ /* turn DS segment override prefix into lock prefix */
text_poke(*ptr, ((unsigned char []){0xf0}), 1); text_poke(ptr, ((unsigned char []){0xf0}), 1);
}; };
mutex_unlock(&text_mutex); mutex_unlock(&text_mutex);
} }
static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end) static void alternatives_smp_unlock(const s32 *start, const s32 *end,
u8 *text, u8 *text_end)
{ {
u8 **ptr; const s32 *poff;
if (noreplace_smp) if (noreplace_smp)
return; return;
mutex_lock(&text_mutex); mutex_lock(&text_mutex);
for (ptr = start; ptr < end; ptr++) { for (poff = start; poff < end; poff++) {
if (*ptr < text) u8 *ptr = (u8 *)poff + *poff;
continue;
if (*ptr > text_end) if (!*poff || ptr < text || ptr >= text_end)
continue; continue;
/* turn lock prefix into DS segment override prefix */ /* turn lock prefix into DS segment override prefix */
text_poke(*ptr, ((unsigned char []){0x3E}), 1); text_poke(ptr, ((unsigned char []){0x3E}), 1);
}; };
mutex_unlock(&text_mutex); mutex_unlock(&text_mutex);
} }
@ -276,8 +278,8 @@ struct smp_alt_module {
char *name; char *name;
/* ptrs to lock prefixes */ /* ptrs to lock prefixes */
u8 **locks; const s32 *locks;
u8 **locks_end; const s32 *locks_end;
/* .text segment, needed to avoid patching init code ;) */ /* .text segment, needed to avoid patching init code ;) */
u8 *text; u8 *text;
@ -398,16 +400,19 @@ void alternatives_smp_switch(int smp)
int alternatives_text_reserved(void *start, void *end) int alternatives_text_reserved(void *start, void *end)
{ {
struct smp_alt_module *mod; struct smp_alt_module *mod;
u8 **ptr; const s32 *poff;
u8 *text_start = start; u8 *text_start = start;
u8 *text_end = end; u8 *text_end = end;
list_for_each_entry(mod, &smp_alt_modules, next) { list_for_each_entry(mod, &smp_alt_modules, next) {
if (mod->text > text_end || mod->text_end < text_start) if (mod->text > text_end || mod->text_end < text_start)
continue; continue;
for (ptr = mod->locks; ptr < mod->locks_end; ptr++) for (poff = mod->locks; poff < mod->locks_end; poff++) {
if (text_start <= *ptr && text_end >= *ptr) const u8 *ptr = (const u8 *)poff + *poff;
if (text_start <= ptr && text_end > ptr)
return 1; return 1;
}
} }
return 0; return 0;