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Commit 5967ed87 authored by Jan Beulich's avatar Jan Beulich Committed by H. Peter Anvin
Browse files

x86-64: Reduce SMP locks table size 



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

Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
LKML-Reference: <4BCF30FE020000780003B3B6@vpn.id2.novell.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 402af0d7

arch/x86/include/asm/alternative-asm.h

+2 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/alternative.h

+2 −2
Original line number Diff line number Diff line
@@ -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; "

arch/x86/kernel/alternative.c

+25 −20
Original line number Diff line number Diff line
@@ -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;
@@ -398,17 +400,20 @@ 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;

}