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Commit bf0c7c34 authored by Waiman Long's avatar Waiman Long Committed by Ingo Molnar
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locking/pvqspinlock, x86: Enable PV qspinlock for KVM 



This patch adds the necessary KVM specific code to allow KVM to
support the CPU halting and kicking operations needed by the queue
spinlock PV code.

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/1429901803-29771-11-git-send-email-Waiman.Long@hp.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f233f7f1

arch/x86/kernel/kvm.c

+43 −0
Original line number Diff line number Diff line
@@ -584,6 +584,39 @@ static void kvm_kick_cpu(int cpu) 
	kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);

}





#ifdef CONFIG_QUEUED_SPINLOCK



#include <asm/qspinlock.h>



static void kvm_wait(u8 *ptr, u8 val)

{

	unsigned long flags;



	if (in_nmi())

		return;



	local_irq_save(flags);



	if (READ_ONCE(*ptr) != val)

		goto out;



	/*

	 * halt until it's our turn and kicked. Note that we do safe halt

	 * for irq enabled case to avoid hang when lock info is overwritten

	 * in irq spinlock slowpath and no spurious interrupt occur to save us.

	 */

	if (arch_irqs_disabled_flags(flags))

		halt();

	else

		safe_halt();



out:

	local_irq_restore(flags);

}



#else /* !CONFIG_QUEUED_SPINLOCK */



enum kvm_contention_stat {

	TAKEN_SLOW,

	TAKEN_SLOW_PICKUP,
@@ -817,6 +850,8 @@ static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket) 
	}

}



#endif /* !CONFIG_QUEUED_SPINLOCK */



/*

 * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.

 */
@@ -828,8 +863,16 @@ void __init kvm_spinlock_init(void) 
	if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))

		return;



#ifdef CONFIG_QUEUED_SPINLOCK

	__pv_init_lock_hash();

	pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;

	pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);

	pv_lock_ops.wait = kvm_wait;

	pv_lock_ops.kick = kvm_kick_cpu;

#else /* !CONFIG_QUEUED_SPINLOCK */

	pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);

	pv_lock_ops.unlock_kick = kvm_unlock_kick;

#endif

}



static __init int kvm_spinlock_init_jump(void)

kernel/Kconfig.locks

+1 −1
Original line number Diff line number Diff line
@@ -240,7 +240,7 @@ config ARCH_USE_QUEUED_SPINLOCK 


config QUEUED_SPINLOCK

	def_bool y if ARCH_USE_QUEUED_SPINLOCK

	depends on SMP && !PARAVIRT_SPINLOCKS

	depends on SMP && (!PARAVIRT_SPINLOCKS || !XEN)



config ARCH_USE_QUEUE_RWLOCK

	bool