1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_QSPINLOCK_PARAVIRT_H
3 #define __ASM_QSPINLOCK_PARAVIRT_H
4 
5 #include <asm/ibt.h>
6 
7 /*
8  * For x86-64, PV_CALLEE_SAVE_REGS_THUNK() saves and restores 8 64-bit
9  * registers. For i386, however, only 1 32-bit register needs to be saved
10  * and restored. So an optimized version of __pv_queued_spin_unlock() is
11  * hand-coded for 64-bit, but it isn't worthwhile to do it for 32-bit.
12  */
13 #ifdef CONFIG_64BIT
14 
15 __PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath, ".spinlock.text");
16 #define __pv_queued_spin_unlock	__pv_queued_spin_unlock
17 #define PV_UNLOCK		"__raw_callee_save___pv_queued_spin_unlock"
18 #define PV_UNLOCK_SLOWPATH	"__raw_callee_save___pv_queued_spin_unlock_slowpath"
19 
20 /*
21  * Optimized assembly version of __raw_callee_save___pv_queued_spin_unlock
22  * which combines the registers saving trunk and the body of the following
23  * C code.  Note that it puts the code in the .spinlock.text section which
24  * is equivalent to adding __lockfunc in the C code:
25  *
26  * void __lockfunc __pv_queued_spin_unlock(struct qspinlock *lock)
27  * {
28  *	u8 lockval = cmpxchg(&lock->locked, _Q_LOCKED_VAL, 0);
29  *
30  *	if (likely(lockval == _Q_LOCKED_VAL))
31  *		return;
32  *	pv_queued_spin_unlock_slowpath(lock, lockval);
33  * }
34  *
35  * For x86-64,
36  *   rdi = lock              (first argument)
37  *   rsi = lockval           (second argument)
38  *   rdx = internal variable (set to 0)
39  */
40 asm    (".pushsection .spinlock.text;"
41 	".globl " PV_UNLOCK ";"
42 	".type " PV_UNLOCK ", @function;"
43 	".align 4,0x90;"
44 	PV_UNLOCK ": "
45 	ASM_ENDBR
46 	FRAME_BEGIN
47 	"push  %rdx;"
48 	"mov   $0x1,%eax;"
49 	"xor   %edx,%edx;"
50 	LOCK_PREFIX "cmpxchg %dl,(%rdi);"
51 	"cmp   $0x1,%al;"
52 	"jne   .slowpath;"
53 	"pop   %rdx;"
54 	FRAME_END
55 	ASM_RET
56 	".slowpath: "
57 	"push   %rsi;"
58 	"movzbl %al,%esi;"
59 	"call " PV_UNLOCK_SLOWPATH ";"
60 	"pop    %rsi;"
61 	"pop    %rdx;"
62 	FRAME_END
63 	ASM_RET
64 	".size " PV_UNLOCK ", .-" PV_UNLOCK ";"
65 	".popsection");
66 
67 #else /* CONFIG_64BIT */
68 
69 extern void __lockfunc __pv_queued_spin_unlock(struct qspinlock *lock);
70 __PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock, ".spinlock.text");
71 
72 #endif /* CONFIG_64BIT */
73 #endif
74