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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
1: lock
.section .smp_locks,"a"
_ASM_ALIGN
_ASM_PTR 1b
.balign 4
.long 1b - .
.previous
.endm
#else

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

@ -30,8 +30,8 @@
#ifdef CONFIG_SMP
#define LOCK_PREFIX \
".section .smp_locks,\"a\"\n" \
_ASM_ALIGN "\n" \
_ASM_PTR "661f\n" /* address */ \
".balign 4\n" \
".long 661f - .\n" /* offset */ \
".previous\n" \
"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 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);
/* 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
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);
for (ptr = start; ptr < end; ptr++) {
if (*ptr < text)
continue;
if (*ptr > text_end)
for (poff = start; poff < end; poff++) {
u8 *ptr = (u8 *)poff + *poff;
if (!*poff || ptr < text || ptr >= text_end)
continue;
/* 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);
}
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)
return;
mutex_lock(&text_mutex);
for (ptr = start; ptr < end; ptr++) {
if (*ptr < text)
continue;
if (*ptr > text_end)
for (poff = start; poff < end; poff++) {
u8 *ptr = (u8 *)poff + *poff;
if (!*poff || ptr < text || ptr >= text_end)
continue;
/* 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);
}
@ -276,8 +278,8 @@ struct smp_alt_module {
char *name;
/* ptrs to lock prefixes */
u8 **locks;
u8 **locks_end;
const s32 *locks;
const s32 *locks_end;
/* .text segment, needed to avoid patching init code ;) */
u8 *text;
@ -398,16 +400,19 @@ void alternatives_smp_switch(int smp)
int alternatives_text_reserved(void *start, void *end)
{
struct smp_alt_module *mod;
u8 **ptr;
const s32 *poff;
u8 *text_start = start;
u8 *text_end = end;
list_for_each_entry(mod, &smp_alt_modules, next) {
if (mod->text > text_end || mod->text_end < text_start)
continue;
for (ptr = mod->locks; ptr < mod->locks_end; ptr++)
if (text_start <= *ptr && text_end >= *ptr)
for (poff = mod->locks; poff < mod->locks_end; poff++) {
const u8 *ptr = (const u8 *)poff + *poff;
if (text_start <= ptr && text_end > ptr)
return 1;
}
}
return 0;