On 26/10/20 18:53, David Woodhouse wrote: > From: David Woodhouse <[email protected]> > > 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.
This looks good, though of course it depends on the somewhat hackish patch 1. However don't you need to read the eventfd as well, since userspace will never be able to do so? Paolo > Signed-off-by: David Woodhouse <[email protected]> > --- > virt/kvm/eventfd.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c > index d6408bb497dc..39443e2f72bf 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 */ >
