On 6 November 2020 16:32:00 GMT, Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: >On Fri, 6 Nov 2020 11:17:21 +0100 >Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > >> On 04/11/20 10:35, David Woodhouse wrote: >> > 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? >> > >> >> Queued, except for patch 2/3 in the eventfd series which Alex hasn't >> reviewed/acked yet. > >There was no vfio patch here, nor mention why it got dropped in v2 >afaict. Thanks, That was a different (but related) series. The VFIO one is https://patchwork.kernel.org/project/kvm/patch/20201027135523.646811-3-dwmw2@xxxxxxxxxxxxx/ Thanks. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
