IRQFD currently uses a deferred workqueue item to execute the injection
operation. It was originally designed this way because kvm_set_irq()
required the caller to hold the irq_lock mutex, and the eventfd callback
is invoked from within a non-preemptible critical section.
With the advent of lockless injection support in kvm_set_irq, the deferment
mechanism is no longer technically needed. Since context switching to the
workqueue is a source of interrupt latency, lets switch to a direct
method.
Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
---
virt/kvm/eventfd.c | 15 +++------------
1 files changed, 3 insertions(+), 12 deletions(-)
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 30f70fd..1a529d4 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -49,16 +49,14 @@ struct _irqfd {
poll_table pt;
wait_queue_head_t *wqh;
wait_queue_t wait;
- struct work_struct inject;
struct work_struct shutdown;
};
static struct workqueue_struct *irqfd_cleanup_wq;
static void
-irqfd_inject(struct work_struct *work)
+irqfd_inject(struct _irqfd *irqfd)
{
- struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
struct kvm *kvm = irqfd->kvm;
kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
@@ -80,12 +78,6 @@ irqfd_shutdown(struct work_struct *work)
remove_wait_queue(irqfd->wqh, &irqfd->wait);
/*
- * We know no new events will be scheduled at this point, so block
- * until all previously outstanding events have completed
- */
- flush_work(&irqfd->inject);
-
- /*
* It is now safe to release the object's resources
*/
eventfd_ctx_put(irqfd->eventfd);
@@ -126,7 +118,7 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
if (flags & POLLIN)
/* An event has been signaled, inject an interrupt */
- schedule_work(&irqfd->inject);
+ irqfd_inject(irqfd);
if (flags & POLLHUP) {
/* The eventfd is closing, detach from KVM */
@@ -179,7 +171,6 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
irqfd->kvm = kvm;
irqfd->gsi = gsi;
INIT_LIST_HEAD(&irqfd->list);
- INIT_WORK(&irqfd->inject, irqfd_inject);
INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
file = eventfd_fget(fd);
@@ -214,7 +205,7 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
* before we registered, and trigger it as if we didn't miss it.
*/
if (events & POLLIN)
- schedule_work(&irqfd->inject);
+ irqfd_inject(irqfd);
/*
* do not drop the file until the irqfd is fully initialized, otherwise
--
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