1/* SPDX-License-Identifier: GPL-2.0-only */
2#include <linux/linkage.h>
3#include <asm/percpu.h>
4
5.text
6
7/*
8 * Inputs:
9 * %rsi : memory location to compare
10 * %rax : low 64 bits of old value
11 * %rdx : high 64 bits of old value
12 * %rbx : low 64 bits of new value
13 * %rcx : high 64 bits of new value
14 * %al  : Operation successful
15 */
16SYM_FUNC_START(this_cpu_cmpxchg16b_emu)
17
18#
19# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not
20# via the ZF.  Caller will access %al to get result.
21#
22# Note that this is only useful for a cpuops operation.  Meaning that we
23# do *not* have a fully atomic operation but just an operation that is
24# *atomic* on a single cpu (as provided by the this_cpu_xx class of
25# macros).
26#
27	pushfq
28	cli
29
30	cmpq PER_CPU_VAR((%rsi)), %rax
31	jne .Lnot_same
32	cmpq PER_CPU_VAR(8(%rsi)), %rdx
33	jne .Lnot_same
34
35	movq %rbx, PER_CPU_VAR((%rsi))
36	movq %rcx, PER_CPU_VAR(8(%rsi))
37
38	popfq
39	mov $1, %al
40	RET
41
42.Lnot_same:
43	popfq
44	xor %al,%al
45	RET
46
47SYM_FUNC_END(this_cpu_cmpxchg16b_emu)
48