To speed up paravirtualized spinlock handling when running on bare
metal introduce a new pvops function "clear_slowpath". This is a nop
when the kernel is running on bare metal.
As the clear_slowpath function is common for all users add a new
initialization function to set the pvops function pointer in order
to avoid spreading the knowledge which function to use.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
arch/x86/include/asm/paravirt.h | 7 +++++++
arch/x86/include/asm/paravirt_types.h | 1 +
arch/x86/include/asm/spinlock.h | 18 ++++--------------
arch/x86/kernel/kvm.c | 2 ++
arch/x86/kernel/paravirt-spinlocks.c | 22 ++++++++++++++++++++++
arch/x86/xen/spinlock.c | 2 ++
6 files changed, 38 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 8957810..318f077 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -724,6 +724,13 @@ static __always_inline void __ticket_unlock_kick(struct arch_spinlock *lock,
PVOP_VCALL2(pv_lock_ops.unlock_kick, lock, ticket);
}
+static __always_inline void __ticket_clear_slowpath(arch_spinlock_t *lock,
+ __ticket_t head)
+{
+ PVOP_VCALL2(pv_lock_ops.clear_slowpath, lock, head);
+}
+
+void pv_lock_activate(void);
#endif
#ifdef CONFIG_X86_32
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index f7b0b5c..3432713 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -336,6 +336,7 @@ typedef u16 __ticket_t;
struct pv_lock_ops {
struct paravirt_callee_save lock_spinning;
void (*unlock_kick)(struct arch_spinlock *lock, __ticket_t ticket);
+ void (*clear_slowpath)(arch_spinlock_t *lock, __ticket_t head);
};
/* This contains all the paravirt structures: we get a convenient
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 268b9da..ab76c3e 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -60,26 +60,16 @@ static inline void __ticket_unlock_kick(arch_spinlock_t *lock,
{
}
+static inline void __ticket_clear_slowpath(arch_spinlock_t *lock,
+ __ticket_t head)
+{
+}
#endif /* CONFIG_PARAVIRT_SPINLOCKS */
static inline int __tickets_equal(__ticket_t one, __ticket_t two)
{
return !((one ^ two) & ~TICKET_SLOWPATH_FLAG);
}
-static inline void __ticket_clear_slowpath(arch_spinlock_t *lock,
- __ticket_t head)
-{
- arch_spinlock_t old, new;
-
- old.tickets.head = head;
- new.tickets.head = head & ~TICKET_SLOWPATH_FLAG;
- old.tickets.tail = new.tickets.head + TICKET_LOCK_INC;
- new.tickets.tail = old.tickets.tail;
-
- /* try to clear slowpath flag when there are no contenders */
- cmpxchg(&lock->head_tail, old.head_tail, new.head_tail);
-}
-
static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{
return __tickets_equal(lock.tickets.head, lock.tickets.tail);
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 9435620..c3b4b43 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -830,6 +830,8 @@ void __init kvm_spinlock_init(void)
pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
pv_lock_ops.unlock_kick = kvm_unlock_kick;
+
+ pv_lock_activate();
}
static __init int kvm_spinlock_init_jump(void)
diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index bbb6c73..5ece813 100644
--- a/arch/x86/kernel/paravirt-spinlocks.c
+++ b/arch/x86/kernel/paravirt-spinlocks.c
@@ -8,10 +8,32 @@
#include <asm/paravirt.h>
+#ifdef CONFIG_SMP
+static void pv_ticket_clear_slowpath(arch_spinlock_t *lock, __ticket_t head)
+{
+ arch_spinlock_t old, new;
+
+ old.tickets.head = head;
+ new.tickets.head = head & ~TICKET_SLOWPATH_FLAG;
+ old.tickets.tail = new.tickets.head + TICKET_LOCK_INC;
+ new.tickets.tail = old.tickets.tail;
+
+ /* try to clear slowpath flag when there are no contenders */
+ cmpxchg(&lock->head_tail, old.head_tail, new.head_tail);
+}
+
+void pv_lock_activate(void)
+{
+ pv_lock_ops.clear_slowpath = pv_ticket_clear_slowpath;
+}
+EXPORT_SYMBOL_GPL(pv_lock_activate);
+#endif
+
struct pv_lock_ops pv_lock_ops = {
#ifdef CONFIG_SMP
.lock_spinning = __PV_IS_CALLEE_SAVE(paravirt_nop),
.unlock_kick = paravirt_nop,
+ .clear_slowpath = paravirt_nop,
#endif
};
EXPORT_SYMBOL(pv_lock_ops);
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 956374c..988c895 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -282,6 +282,8 @@ void __init xen_init_spinlocks(void)
printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning);
pv_lock_ops.unlock_kick = xen_unlock_kick;
+
+ pv_lock_activate();
}
/*
--
2.1.4
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