On Wed, 2020-10-28 at 15:35 +0100, Peter Zijlstra wrote: > On Tue, Oct 27, 2020 at 02:39:43PM +0000, David Woodhouse wrote: > > From: David Woodhouse <dwmw@xxxxxxxxxxxx> > > > > This allows an exclusive wait_queue_entry to be added at the head of the > > queue, instead of the tail as normal. Thus, it gets to consume events > > first without allowing non-exclusive waiters to be woken at all. > > > > The (first) intended use is for KVM IRQFD, which currently has > > inconsistent behaviour depending on whether posted interrupts are > > available or not. If they are, KVM will bypass the eventfd completely > > and deliver interrupts directly to the appropriate vCPU. If not, events > > are delivered through the eventfd and userspace will receive them when > > polling on the eventfd. > > > > By using add_wait_queue_priority(), KVM will be able to consistently > > consume events within the kernel without accidentally exposing them > > to userspace when they're supposed to be bypassed. This, in turn, means > > that userspace doesn't have to jump through hoops to avoid listening > > on the erroneously noisy eventfd and injecting duplicate interrupts. > > > > Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> > > Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Thanks. Paolo, the conclusion was that you were going to take this set through the KVM tree, wasn't it?
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