1 files changed, 66 insertions, 0 deletions
diff --git a/arch/x86/include/asm/qspinlock_paravirt.h b/arch/x86/include/asm/qspinlock_paravirt.h
new file mode 100644
index 000000000..42b17cf10
--- /dev/null
+++ b/arch/x86/include/asm/qspinlock_paravirt.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_QSPINLOCK_PARAVIRT_H
+#define __ASM_QSPINLOCK_PARAVIRT_H
+
+#include <asm/ibt.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, ".spinlock.text");
+#define __pv_queued_spin_unlock	__pv_queued_spin_unlock
+
+/*
+ * 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.  Note that it puts the code in the .spinlock.text section which
+ * is equivalent to adding __lockfunc in the C code:
+ *
+ * void __lockfunc __pv_queued_spin_unlock(struct qspinlock *lock)
+ * {
+ *	u8 lockval = cmpxchg(&lock->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)
+ */
+#define PV_UNLOCK_ASM							\
+	FRAME_BEGIN							\
+	"push  %rdx\n\t"						\
+	"mov   $0x1,%eax\n\t"						\
+	"xor   %edx,%edx\n\t"						\
+	LOCK_PREFIX "cmpxchg %dl,(%rdi)\n\t"				\
+	"cmp   $0x1,%al\n\t"						\
+	"jne   .slowpath\n\t"						\
+	"pop   %rdx\n\t"						\
+	FRAME_END							\
+	ASM_RET								\
+	".slowpath:\n\t"						\
+	"push   %rsi\n\t"						\
+	"movzbl %al,%esi\n\t"						\
+	"call __raw_callee_save___pv_queued_spin_unlock_slowpath\n\t"	\
+	"pop    %rsi\n\t"						\
+	"pop    %rdx\n\t"						\
+	FRAME_END
+
+DEFINE_PARAVIRT_ASM(__raw_callee_save___pv_queued_spin_unlock,
+		    PV_UNLOCK_ASM, .spinlock.text);
+
+#else /* CONFIG_64BIT */
+
+extern void __lockfunc __pv_queued_spin_unlock(struct qspinlock *lock);
+__PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock, ".spinlock.text");
+
+#endif /* CONFIG_64BIT */
+#endif