diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2020-10-26 17:53:25 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-11-15 09:49:10 -0500 |
| commit | e8dbf19508a112d125190df77ee0464b7ba56192 (patch) | |
| tree | 0abf8e1b860f762db6122894c02192b1bff8630f | |
| parent | c4d51a52c67a1e3a0fa3006e5ec21cdc07649cd6 (diff) | |
| download | lwn-e8dbf19508a112d125190df77ee0464b7ba56192.tar.gz lwn-e8dbf19508a112d125190df77ee0464b7ba56192.zip | |
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 <dwmw@amazon.co.uk>
Message-Id: <20201026175325.585623-2-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | virt/kvm/eventfd.c | 6 |
1 files changed, 4 insertions, 2 deletions
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 */ |