[PATCH V12 10/14] RISC-V: paravirt: Add pvqspinlock frontend skeleton

[guoren at kernel.org]

From: Guo Ren <guoren at linux.alibaba.com>

Using static_call to switch between:
  native_queued_spin_lock_slowpath()    __pv_queued_spin_lock_slowpath()
  native_queued_spin_unlock()           __pv_queued_spin_unlock()

Finish the pv_wait implementation, but pv_kick needs the SBI
definition of the next patches.

Reviewed-by: Leonardo Bras <leobras at redhat.com>
Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
---
 arch/riscv/include/asm/Kbuild               |  1 -
 arch/riscv/include/asm/qspinlock.h          | 35 +++++++++++++
 arch/riscv/include/asm/qspinlock_paravirt.h | 29 +++++++++++
 arch/riscv/kernel/qspinlock_paravirt.c      | 57 +++++++++++++++++++++
 arch/riscv/kernel/setup.c                   |  4 ++
 5 files changed, 125 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/include/asm/qspinlock.h
 create mode 100644 arch/riscv/include/asm/qspinlock_paravirt.h
 create mode 100644 arch/riscv/kernel/qspinlock_paravirt.c

diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index ad72f2bd4cc9..85a428ad116d 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -8,6 +8,5 @@ generic-y += spinlock_types.h
 generic-y += ticket_spinlock.h
 generic-y += qrwlock.h
 generic-y += qrwlock_types.h
-generic-y += qspinlock.h
 generic-y += user.h
 generic-y += vmlinux.lds.h
diff --git a/arch/riscv/include/asm/qspinlock.h b/arch/riscv/include/asm/qspinlock.h
new file mode 100644
index 000000000000..02ce973b5b6e
--- /dev/null
+++ b/arch/riscv/include/asm/qspinlock.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c), 2023 Alibaba
+ * Authors:
+ *	Guo Ren <guoren at linux.alibaba.com>
+ */
+
+#ifndef _ASM_RISCV_QSPINLOCK_H
+#define _ASM_RISCV_QSPINLOCK_H
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+#include <asm/qspinlock_paravirt.h>
+
+/* How long a lock should spin before we consider blocking */
+#define SPIN_THRESHOLD		(1 << 15)
+
+void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+void __pv_init_lock_hash(void);
+void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+
+static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
+{
+	static_call(pv_queued_spin_lock_slowpath)(lock, val);
+}
+
+#define queued_spin_unlock	queued_spin_unlock
+static inline void queued_spin_unlock(struct qspinlock *lock)
+{
+	static_call(pv_queued_spin_unlock)(lock);
+}
+#endif /* CONFIG_PARAVIRT_SPINLOCKS */
+
+#include <asm-generic/qspinlock.h>
+
+#endif /* _ASM_RISCV_QSPINLOCK_H */
diff --git a/arch/riscv/include/asm/qspinlock_paravirt.h b/arch/riscv/include/asm/qspinlock_paravirt.h
new file mode 100644
index 000000000000..9681e851f69d
--- /dev/null
+++ b/arch/riscv/include/asm/qspinlock_paravirt.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c), 2023 Alibaba Cloud
+ * Authors:
+ *	Guo Ren <guoren at linux.alibaba.com>
+ */
+
+#ifndef _ASM_RISCV_QSPINLOCK_PARAVIRT_H
+#define _ASM_RISCV_QSPINLOCK_PARAVIRT_H
+
+void pv_wait(u8 *ptr, u8 val);
+void pv_kick(int cpu);
+
+void dummy_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+void dummy_queued_spin_unlock(struct qspinlock *lock);
+
+DECLARE_STATIC_CALL(pv_queued_spin_lock_slowpath, dummy_queued_spin_lock_slowpath);
+DECLARE_STATIC_CALL(pv_queued_spin_unlock, dummy_queued_spin_unlock);
+
+void __init pv_qspinlock_init(void);
+
+static inline bool pv_is_native_spin_unlock(void)
+{
+	return false;
+}
+
+void __pv_queued_spin_unlock(struct qspinlock *lock);
+
+#endif /* _ASM_RISCV_QSPINLOCK_PARAVIRT_H */
diff --git a/arch/riscv/kernel/qspinlock_paravirt.c b/arch/riscv/kernel/qspinlock_paravirt.c
new file mode 100644
index 000000000000..85ff5a3ec234
--- /dev/null
+++ b/arch/riscv/kernel/qspinlock_paravirt.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c), 2023 Alibaba Cloud
+ * Authors:
+ *	Guo Ren <guoren at linux.alibaba.com>
+ */
+
+#include <linux/static_call.h>
+#include <asm/qspinlock_paravirt.h>
+#include <asm/sbi.h>
+
+void pv_kick(int cpu)
+{
+	return;
+}
+
+void pv_wait(u8 *ptr, u8 val)
+{
+	unsigned long flags;
+
+	if (in_nmi())
+		return;
+
+	local_irq_save(flags);
+	if (READ_ONCE(*ptr) != val)
+		goto out;
+
+	/* wait_for_interrupt(); */
+out:
+	local_irq_restore(flags);
+}
+
+static void native_queued_spin_unlock(struct qspinlock *lock)
+{
+	smp_store_release(&lock->locked, 0);
+}
+
+DEFINE_STATIC_CALL(pv_queued_spin_lock_slowpath, native_queued_spin_lock_slowpath);
+EXPORT_STATIC_CALL(pv_queued_spin_lock_slowpath);
+
+DEFINE_STATIC_CALL(pv_queued_spin_unlock, native_queued_spin_unlock);
+EXPORT_STATIC_CALL(pv_queued_spin_unlock);
+
+void __init pv_qspinlock_init(void)
+{
+	if (num_possible_cpus() == 1)
+		return;
+
+	if(sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)
+		return;
+
+	pr_info("PV qspinlocks enabled\n");
+	__pv_init_lock_hash();
+
+	static_call_update(pv_queued_spin_lock_slowpath, __pv_queued_spin_lock_slowpath);
+	static_call_update(pv_queued_spin_unlock, __pv_queued_spin_unlock);
+}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index e33430e9d97e..052bbfbb7f32 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -304,6 +304,10 @@ static void __init riscv_spinlock_init(void)
 #ifdef CONFIG_QUEUED_SPINLOCKS
 	virt_spin_lock_init();
 #endif
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+	pv_qspinlock_init();
+#endif
 }
 #endif
 
-- 
2.40.1