From e8dbf19508a112d125190df77ee0464b7ba56192 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Mon, 26 Oct 2020 17:53:25 +0000 Subject: kvm/eventfd: Use priority waitqueue to catch events before userspace As far as I can tell, when we use posted interrupts we silently cut off the events from userspace, if it's listening on the same eventfd that feeds the irqfd. I like that behaviour. Let's do it all the time, even without posted interrupts. It makes it much easier to handle IRQ remapping invalidation without having to constantly add/remove the fd from the userspace poll set. We can just leave userspace polling on it, and the bypass will... well... bypass it. Signed-off-by: David Woodhouse Message-Id: <20201026175325.585623-2-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini --- virt/kvm/eventfd.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'virt') diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index c2323c27a28b..efa8a5ae7a95 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -191,6 +191,7 @@ irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) struct kvm *kvm = irqfd->kvm; unsigned seq; int idx; + int ret = 0; if (flags & EPOLLIN) { idx = srcu_read_lock(&kvm->irq_srcu); @@ -204,6 +205,7 @@ irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) false) == -EWOULDBLOCK) schedule_work(&irqfd->inject); srcu_read_unlock(&kvm->irq_srcu, idx); + ret = 1; } if (flags & EPOLLHUP) { @@ -227,7 +229,7 @@ irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) spin_unlock_irqrestore(&kvm->irqfds.lock, iflags); } - return 0; + return ret; } static void @@ -236,7 +238,7 @@ irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh, { struct kvm_kernel_irqfd *irqfd = container_of(pt, struct kvm_kernel_irqfd, pt); - add_wait_queue(wqh, &irqfd->wait); + add_wait_queue_priority(wqh, &irqfd->wait); } /* Must be called under irqfds.lock */ -- cgit v1.2.3