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: Bhaktipriya Shridhar <[email protected]> --- virt/kvm/arm/arch_timer.c | 11 ++--------- virt/kvm/eventfd.c | 22 +++------------------- virt/kvm/kvm_main.c | 6 ------ 3 files changed, 5 insertions(+), 34 deletions(-) diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index e2d5b6f..56e0c15 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -31,7 +31,6 @@ #include "trace.h" static struct timecounter *timecounter; -static struct workqueue_struct *wqueue; static unsigned int host_vtimer_irq; void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu) @@ -140,7 +139,7 @@ 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; } @@ -455,12 +454,6 @@ int kvm_timer_hyp_init(void) goto out_free; } - wqueue = create_singlethread_workqueue("kvm_arch_timer"); - if (!wqueue) { - err = -ENOMEM; - goto out_free; - } - kvm_info("virtual timer IRQ%d\n", host_vtimer_irq); on_each_cpu(kvm_timer_init_interrupt, NULL, 1); @@ -522,7 +515,7 @@ 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; diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index e469b60..f397e9b 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -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 diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 02e98f3..93506d2 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3719,12 +3719,7 @@ 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; @@ -3805,7 +3800,6 @@ out_free_0a: free_cpumask_var(cpus_hardware_enabled); out_free_0: kvm_irqfd_exit(); -out_irqfd: kvm_arch_exit(); out_fail: return r; -- 2.1.4
