Commit 3706feac authored by Bhaktipriya Shridhar's avatar Bhaktipriya Shridhar Committed by Paolo Bonzini
Browse files

KVM: Remove deprecated create_singlethread_workqueue 



The workqueue "irqfd_cleanup_wq" queues a single work item
&irqfd->shutdown and hence doesn't require ordering. It is a host-wide
workqueue for issuing deferred shutdown requests aggregated from all
vm* instances. It is not being used on a memory reclaim path.
Hence, it has been converted to use system_wq.
The work item has been flushed in kvm_irqfd_release().

The workqueue "wqueue" queues a single work item &timer->expired
and hence doesn't require ordering. Also, it is not being used on
a memory reclaim path. Hence, it has been converted to use system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

Signed-off-by: default avatarBhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f15a75ee

virt/kvm/arm/arch_timer.c

+2 −9
Original line number Diff line number Diff line
@@ -31,7 +31,6 @@ 
#include "trace.h"



static struct timecounter *timecounter;

static struct workqueue_struct *wqueue;

static unsigned int host_vtimer_irq;

static u32 host_vtimer_irq_flags;
@@ -141,7 +140,7 @@ static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt) 
		return HRTIMER_RESTART;

	}



	queue_work(wqueue, &timer->expired);

	schedule_work(&timer->expired);

	return HRTIMER_NORESTART;

}
@@ -449,12 +448,6 @@ int kvm_timer_hyp_init(void) 
		goto out;

	}



	wqueue = create_singlethread_workqueue("kvm_arch_timer");

	if (!wqueue) {

		err = -ENOMEM;

		goto out_free;

	}



	kvm_info("virtual timer IRQ%d\n", host_vtimer_irq);



	cpuhp_setup_state(CPUHP_AP_KVM_ARM_TIMER_STARTING,
@@ -518,7 +511,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu) 
	 * VCPUs have the enabled variable set, before entering the guest, if

	 * the arch timers are enabled.

	 */

	if (timecounter && wqueue)

	if (timecounter)

		timer->enabled = 1;



	return 0;

virt/kvm/eventfd.c

+3 −19
Original line number Diff line number Diff line
@@ -42,7 +42,6 @@ 


#ifdef CONFIG_HAVE_KVM_IRQFD



static struct workqueue_struct *irqfd_cleanup_wq;



static void

irqfd_inject(struct work_struct *work)
@@ -168,7 +167,7 @@ irqfd_deactivate(struct kvm_kernel_irqfd *irqfd) 


	list_del_init(&irqfd->list);



	queue_work(irqfd_cleanup_wq, &irqfd->shutdown);

	schedule_work(&irqfd->shutdown);

}



int __attribute__((weak)) kvm_arch_set_irq_inatomic(
@@ -555,7 +554,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args) 
	 * so that we guarantee there will not be any more interrupts on this

	 * gsi once this deassign function returns.

	 */

	flush_workqueue(irqfd_cleanup_wq);

	flush_work(&irqfd->shutdown);



	return 0;

}
@@ -592,7 +591,7 @@ kvm_irqfd_release(struct kvm *kvm) 
	 * Block until we know all outstanding shutdown jobs have completed

	 * since we do not take a kvm* reference.

	 */

	flush_workqueue(irqfd_cleanup_wq);

	flush_work(&irqfd->shutdown);



}
@@ -622,23 +621,8 @@ void kvm_irq_routing_update(struct kvm *kvm) 
	spin_unlock_irq(&kvm->irqfds.lock);

}



/*

 * create a host-wide workqueue for issuing deferred shutdown requests

 * aggregated from all vm* instances. We need our own isolated single-thread

 * queue to prevent deadlock against flushing the normal work-queue.

 */

int kvm_irqfd_init(void)

{

	irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");

	if (!irqfd_cleanup_wq)

		return -ENOMEM;



	return 0;

}



void kvm_irqfd_exit(void)

{

	destroy_workqueue(irqfd_cleanup_wq);

}

#endif

virt/kvm/kvm_main.c

+0 −6
Original line number Diff line number Diff line
@@ -3807,12 +3807,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, 
	 * kvm_arch_init makes sure there's at most one caller

	 * for architectures that support multiple implementations,

	 * like intel and amd on x86.

	 * kvm_arch_init must be called before kvm_irqfd_init to avoid creating

	 * conflicts in case kvm is already setup for another implementation.

	 */

	r = kvm_irqfd_init();

	if (r)

		goto out_irqfd;



	if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {

		r = -ENOMEM;
@@ -3894,7 +3889,6 @@ out_free_0a: 
	free_cpumask_var(cpus_hardware_enabled);

out_free_0:

	kvm_irqfd_exit();

out_irqfd:

	kvm_arch_exit();

out_fail:

	return r;

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