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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_CMPXCHG_32_H
#define _ASM_X86_CMPXCHG_32_H
/*
* Note: if you use set64_bit(), __cmpxchg64(), or their variants,
* you need to test for the feature in boot_cpu_data.
*/
/*
* CMPXCHG8B only writes to the target if we had the previous
* value in registers, otherwise it acts as a read and gives us the
* "new previous" value. That is why there is a loop. Preloading
* EDX:EAX is a performance optimization: in the common case it means
* we need only one locked operation.
*
* A SIMD/3DNOW!/MMX/FPU 64-bit store here would require at the very
* least an FPU save and/or %cr0.ts manipulation.
*
* cmpxchg8b must be used with the lock prefix here to allow the
* instruction to be executed atomically. We need to have the reader
* side to see the coherent 64bit value.
*/
static inline void set_64bit(volatile u64 *ptr, u64 value)
{
u32 low = value;
u32 high = value >> 32;
u64 prev = *ptr;
asm volatile("\n1:\t"
LOCK_PREFIX "cmpxchg8b %0\n\t"
"jnz 1b"
: "=m" (*ptr), "+A" (prev)
: "b" (low), "c" (high)
: "memory");
}
#ifdef CONFIG_X86_CMPXCHG64
#define arch_cmpxchg64(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
(unsigned long long)(n)))
#define arch_cmpxchg64_local(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg64_local((ptr), (unsigned long long)(o), \
(unsigned long long)(n)))
#endif
static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)
{
u64 prev;
asm volatile(LOCK_PREFIX "cmpxchg8b %1"
: "=A" (prev),
"+m" (*ptr)
: "b" ((u32)new),
"c" ((u32)(new >> 32)),
"0" (old)
: "memory");
return prev;
}
static inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new)
{
u64 prev;
asm volatile("cmpxchg8b %1"
: "=A" (prev),
"+m" (*ptr)
: "b" ((u32)new),
"c" ((u32)(new >> 32)),
"0" (old)
: "memory");
return prev;
}
#ifndef CONFIG_X86_CMPXCHG64
/*
* Building a kernel capable running on 80386 and 80486. It may be necessary
* to simulate the cmpxchg8b on the 80386 and 80486 CPU.
*/
#define arch_cmpxchg64(ptr, o, n) \
({ \
__typeof__(*(ptr)) __ret; \
__typeof__(*(ptr)) __old = (o); \
__typeof__(*(ptr)) __new = (n); \
alternative_io(LOCK_PREFIX_HERE \
"call cmpxchg8b_emu", \
"lock; cmpxchg8b (%%esi)" , \
X86_FEATURE_CX8, \
"=A" (__ret), \
"S" ((ptr)), "0" (__old), \
"b" ((unsigned int)__new), \
"c" ((unsigned int)(__new>>32)) \
: "memory"); \
__ret; })
#define arch_cmpxchg64_local(ptr, o, n) \
({ \
__typeof__(*(ptr)) __ret; \
__typeof__(*(ptr)) __old = (o); \
__typeof__(*(ptr)) __new = (n); \
alternative_io("call cmpxchg8b_emu", \
"cmpxchg8b (%%esi)" , \
X86_FEATURE_CX8, \
"=A" (__ret), \
"S" ((ptr)), "0" (__old), \
"b" ((unsigned int)__new), \
"c" ((unsigned int)(__new>>32)) \
: "memory"); \
__ret; })
#endif
#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
#endif /* _ASM_X86_CMPXCHG_32_H */
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