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Commit f233f7f1 authored by Peter Zijlstra (Intel)'s avatar Peter Zijlstra (Intel) Committed by Ingo Molnar
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locking/pvqspinlock, x86: Implement the paravirt qspinlock call patching 



We use the regular paravirt call patching to switch between:

  native_queued_spin_lock_slowpath()	__pv_queued_spin_lock_slowpath()
  native_queued_spin_unlock()		__pv_queued_spin_unlock()

We use a callee saved call for the unlock function which reduces the
i-cache footprint and allows 'inlining' of SPIN_UNLOCK functions
again.

We further optimize the unlock path by patching the direct call with a
"movb $0,%arg1" if we are indeed using the native unlock code. This
makes the unlock code almost as fast as the !PARAVIRT case.

This significantly lowers the overhead of having
CONFIG_PARAVIRT_SPINLOCKS enabled, even for native code.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarWaiman Long <Waiman.Long@hp.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-10-git-send-email-Waiman.Long@hp.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a23db284

arch/x86/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -667,7 +667,7 @@ config PARAVIRT_DEBUG 
config PARAVIRT_SPINLOCKS

	bool "Paravirtualization layer for spinlocks"

	depends on PARAVIRT && SMP

	select UNINLINE_SPIN_UNLOCK

	select UNINLINE_SPIN_UNLOCK if !QUEUED_SPINLOCK

	---help---

	  Paravirtualized spinlocks allow a pvops backend to replace the

	  spinlock implementation with something virtualization-friendly

arch/x86/include/asm/paravirt.h

+28 −1
Original line number Diff line number Diff line
@@ -712,6 +712,31 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx, 


#if defined(CONFIG_SMP) && defined(CONFIG_PARAVIRT_SPINLOCKS)



#ifdef CONFIG_QUEUED_SPINLOCK



static __always_inline void pv_queued_spin_lock_slowpath(struct qspinlock *lock,

							u32 val)

{

	PVOP_VCALL2(pv_lock_ops.queued_spin_lock_slowpath, lock, val);

}



static __always_inline void pv_queued_spin_unlock(struct qspinlock *lock)

{

	PVOP_VCALLEE1(pv_lock_ops.queued_spin_unlock, lock);

}



static __always_inline void pv_wait(u8 *ptr, u8 val)

{

	PVOP_VCALL2(pv_lock_ops.wait, ptr, val);

}



static __always_inline void pv_kick(int cpu)

{

	PVOP_VCALL1(pv_lock_ops.kick, cpu);

}



#else /* !CONFIG_QUEUED_SPINLOCK */



static __always_inline void __ticket_lock_spinning(struct arch_spinlock *lock,

							__ticket_t ticket)

{
@@ -724,7 +749,9 @@ static __always_inline void __ticket_unlock_kick(struct arch_spinlock *lock, 
	PVOP_VCALL2(pv_lock_ops.unlock_kick, lock, ticket);

}



#endif

#endif /* CONFIG_QUEUED_SPINLOCK */



#endif /* SMP && PARAVIRT_SPINLOCKS */



#ifdef CONFIG_X86_32

#define PV_SAVE_REGS "pushl %ecx; pushl %edx;"

arch/x86/include/asm/paravirt_types.h

+10 −0
Original line number Diff line number Diff line
@@ -333,9 +333,19 @@ struct arch_spinlock; 
typedef u16 __ticket_t;

#endif



struct qspinlock;



struct pv_lock_ops {

#ifdef CONFIG_QUEUED_SPINLOCK

	void (*queued_spin_lock_slowpath)(struct qspinlock *lock, u32 val);

	struct paravirt_callee_save queued_spin_unlock;



	void (*wait)(u8 *ptr, u8 val);

	void (*kick)(int cpu);

#else /* !CONFIG_QUEUED_SPINLOCK */

	struct paravirt_callee_save lock_spinning;

	void (*unlock_kick)(struct arch_spinlock *lock, __ticket_t ticket);

#endif /* !CONFIG_QUEUED_SPINLOCK */

};



/* This contains all the paravirt structures: we get a convenient

arch/x86/include/asm/qspinlock.h

+24 −1
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 


#include <asm/cpufeature.h>

#include <asm-generic/qspinlock_types.h>

#include <asm/paravirt.h>



#define	queued_spin_unlock queued_spin_unlock

/**
@@ -11,11 +12,33 @@ 
 *

 * A smp_store_release() on the least-significant byte.

 */

static inline void queued_spin_unlock(struct qspinlock *lock)

static inline void native_queued_spin_unlock(struct qspinlock *lock)

{

	smp_store_release((u8 *)lock, 0);

}



#ifdef CONFIG_PARAVIRT_SPINLOCKS

extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);

extern void __pv_init_lock_hash(void);

extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);

extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);



static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)

{

	pv_queued_spin_lock_slowpath(lock, val);

}



static inline void queued_spin_unlock(struct qspinlock *lock)

{

	pv_queued_spin_unlock(lock);

}

#else

static inline void queued_spin_unlock(struct qspinlock *lock)

{

	native_queued_spin_unlock(lock);

}

#endif



#define virt_queued_spin_lock virt_queued_spin_lock



static inline bool virt_queued_spin_lock(struct qspinlock *lock)

arch/x86/include/asm/qspinlock_paravirt.h

0 → 100644
+6 −0
Original line number Diff line number Diff line 
#ifndef __ASM_QSPINLOCK_PARAVIRT_H

#define __ASM_QSPINLOCK_PARAVIRT_H



PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock);



#endif