Release 4.14 arch/x86/include/asm/qspinlock_paravirt.h
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_QSPINLOCK_PARAVIRT_H
#define __ASM_QSPINLOCK_PARAVIRT_H
/*
* For x86-64, PV_CALLEE_SAVE_REGS_THUNK() saves and restores 8 64-bit
* registers. For i386, however, only 1 32-bit register needs to be saved
* and restored. So an optimized version of __pv_queued_spin_unlock() is
* hand-coded for 64-bit, but it isn't worthwhile to do it for 32-bit.
*/
#ifdef CONFIG_64BIT
PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath);
#define __pv_queued_spin_unlock __pv_queued_spin_unlock
#define PV_UNLOCK "__raw_callee_save___pv_queued_spin_unlock"
#define PV_UNLOCK_SLOWPATH "__raw_callee_save___pv_queued_spin_unlock_slowpath"
/*
* Optimized assembly version of __raw_callee_save___pv_queued_spin_unlock
* which combines the registers saving trunk and the body of the following
* C code:
*
* void __pv_queued_spin_unlock(struct qspinlock *lock)
* {
* struct __qspinlock *l = (void *)lock;
* u8 lockval = cmpxchg(&l->locked, _Q_LOCKED_VAL, 0);
*
* if (likely(lockval == _Q_LOCKED_VAL))
* return;
* pv_queued_spin_unlock_slowpath(lock, lockval);
* }
*
* For x86-64,
* rdi = lock (first argument)
* rsi = lockval (second argument)
* rdx = internal variable (set to 0)
*/
asm (".pushsection .text;"
".globl " PV_UNLOCK ";"
".type " PV_UNLOCK ", @function;"
".align 4,0x90;"
PV_UNLOCK ": "
FRAME_BEGIN
"push %rdx;"
"mov $0x1,%eax;"
"xor %edx,%edx;"
"lock cmpxchg %dl,(%rdi);"
"cmp $0x1,%al;"
"jne .slowpath;"
"pop %rdx;"
FRAME_END
"ret;"
".slowpath: "
"push %rsi;"
"movzbl %al,%esi;"
"call " PV_UNLOCK_SLOWPATH ";"
"pop %rsi;"
"pop %rdx;"
FRAME_END
"ret;"
".size " PV_UNLOCK ", .-" PV_UNLOCK ";"
".popsection");
#else /* CONFIG_64BIT */
extern void __pv_queued_spin_unlock(struct qspinlock *lock);
PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock);
#endif /* CONFIG_64BIT */
#endif
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