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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_BARRIER_H
#define _ASM_X86_BARRIER_H
#include <asm/alternative.h>
#include <asm/nops.h>
/*
* Force strict CPU ordering.
* And yes, this might be required on UP too when we're talking
* to devices.
*/
#ifdef CONFIG_X86_32
#define mb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "mfence", \
X86_FEATURE_XMM2) ::: "memory", "cc")
#define rmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "lfence", \
X86_FEATURE_XMM2) ::: "memory", "cc")
#define wmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "sfence", \
X86_FEATURE_XMM2) ::: "memory", "cc")
#else
#define __mb() asm volatile("mfence":::"memory")
#define __rmb() asm volatile("lfence":::"memory")
#define __wmb() asm volatile("sfence" ::: "memory")
#endif
/**
* array_index_mask_nospec() - generate a mask that is ~0UL when the
* bounds check succeeds and 0 otherwise
* @index: array element index
* @size: number of elements in array
*
* Returns:
* 0 - (index < size)
*/
static inline unsigned long array_index_mask_nospec(unsigned long index,
unsigned long size)
{
unsigned long mask;
asm volatile ("cmp %1,%2; sbb %0,%0;"
:"=r" (mask)
:"g"(size),"r" (index)
:"cc");
return mask;
}
/* Override the default implementation from linux/nospec.h. */
#define array_index_mask_nospec array_index_mask_nospec
/* Prevent speculative execution past this barrier. */
#define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)
#define __dma_rmb() barrier()
#define __dma_wmb() barrier()
#define __smp_mb() asm volatile("lock; addl $0,-4(%%" _ASM_SP ")" ::: "memory", "cc")
#define __smp_rmb() dma_rmb()
#define __smp_wmb() barrier()
#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
barrier(); \
WRITE_ONCE(*p, v); \
} while (0)
#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
barrier(); \
___p1; \
})
/* Atomic operations are already serializing on x86 */
#define __smp_mb__before_atomic() do { } while (0)
#define __smp_mb__after_atomic() do { } while (0)
#include <asm-generic/barrier.h>
/*
* Make previous memory operations globally visible before
* a WRMSR.
*
* MFENCE makes writes visible, but only affects load/store
* instructions. WRMSR is unfortunately not a load/store
* instruction and is unaffected by MFENCE. The LFENCE ensures
* that the WRMSR is not reordered.
*
* Most WRMSRs are full serializing instructions themselves and
* do not require this barrier. This is only required for the
* IA32_TSC_DEADLINE and X2APIC MSRs.
*/
static inline void weak_wrmsr_fence(void)
{
asm volatile("mfence; lfence" : : : "memory");
}
#endif /* _ASM_X86_BARRIER_H */
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