On Wed, 2012-06-27 at 17:51 +0300, Gleb Natapov wrote: > On Wed, Jun 27, 2012 at 08:29:04AM -0600, Alex Williamson wrote: > > On Wed, 2012-06-27 at 16:58 +0300, Gleb Natapov wrote: > > > On Tue, Jun 26, 2012 at 11:10:08PM -0600, Alex Williamson wrote: > > > > This new ioctl enables an eventfd to be triggered when an EOI is > > > > written for a specified irqchip pin. By default this is a simple > > > > notification, but we can also tie the eoifd to a level irqfd, which > > > > enables the irqchip pin to be automatically de-asserted on EOI. > > > > This mode is particularly useful for device-assignment applications > > > > where the unmask and notify triggers a hardware unmask. The default > > > > mode is most applicable to simple notify with no side-effects for > > > > userspace usage, such as Qemu. > > > > > > > > Here we make use of the reference counting of the _irq_source > > > > object allowing us to share it with an irqfd and cleanup regardless > > > > of the release order. > > > > > > > > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > > --- > > > > > > > > Documentation/virtual/kvm/api.txt | 24 +++++ > > > > arch/x86/kvm/x86.c | 1 > > > > include/linux/kvm.h | 14 +++ > > > > include/linux/kvm_host.h | 13 +++ > > > > virt/kvm/eventfd.c | 189 +++++++++++++++++++++++++++++++++++++ > > > > virt/kvm/kvm_main.c | 11 ++ > > > > 6 files changed, 250 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt > > > > index b216709..87a2558 100644 > > > > --- a/Documentation/virtual/kvm/api.txt > > > > +++ b/Documentation/virtual/kvm/api.txt > > > > @@ -1987,6 +1987,30 @@ interrupts with those injected through KVM_IRQ_LINE. IRQFDs created > > > > with KVM_IRQFD_FLAG_LEVEL must also set this flag when de-assiging. > > > > KVM_IRQFD_FLAG_LEVEL support is indicated by KVM_CAP_IRQFD_LEVEL. > > > > > > > > +4.77 KVM_EOIFD > > > > + > > > > +Capability: KVM_CAP_EOIFD > > > > +Architectures: x86 > > > > +Type: vm ioctl > > > > +Parameters: struct kvm_eoifd (in) > > > > +Returns: 0 on success, -1 on error > > > > + > > > > +KVM_EOIFD allows userspace to receive EOI notification through an > > > > +eventfd for level triggered irqchip interrupts. Behavior for edge > > > > +triggered interrupts is undefined. kvm_eoifd.fd specifies the eventfd > > > Lets make it defined. EOI notification can be used by userspace to fix > > > time drift due to lost interrupts. But than userspace needs to know > > > which vcpu did EOI. > > > > Hmm, do we need an additional flag and field in kvm_eoifd to filter by > > vCPU then? > > > This will be enough for a use case I am aware of. Don't know if this > interface is generic enough for all possible use cases. That's generally a hard prediction to make ;) We currently don't pass a kvm_vcpu anywhere close to the irq ack notifier. The ioapic path could be relatively trivial, but the pic path is a bit further disconnected. If we had that plumbing, a KVM_CAP plus vcpu filter flag and specifying the vcpu using some of the padding space seems like it's sufficient. I'll drop mention of level-only from the description, but the plumbing and vcpu filtering can be a follow-on. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
