kvm/eventfd: Use priority waitqueue to catch events before userspace (e8dbf195) · Commits · 戴 / test

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 <dwmw@amazon.co.uk> Message-Id: <20201026175325.585623-2-dwmw2@infradead.org> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

virt/kvm/eventfd.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -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 */

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