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    SubjectRe: [PATCH 2/4] kvm: Add missing KVM_IRQFD API documentation
    On Sun, Jun 24, 2012 at 08:56:17AM -0600, Alex Williamson wrote:
    > On Sun, 2012-06-24 at 11:34 +0300, Michael S. Tsirkin wrote:
    > > On Fri, Jun 22, 2012 at 04:15:50PM -0600, Alex Williamson wrote:
    > > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
    > > > ---
    > > >
    > > > Documentation/virtual/kvm/api.txt | 17 +++++++++++++++++
    > > > 1 file changed, 17 insertions(+)
    > > >
    > > > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
    > > > index 310fe50..9b4cb2b 100644
    > > > --- a/Documentation/virtual/kvm/api.txt
    > > > +++ b/Documentation/virtual/kvm/api.txt
    > > > @@ -1965,6 +1965,23 @@ return the hash table order in the parameter. (If the guest is using
    > > > the virtualized real-mode area (VRMA) facility, the kernel will
    > > > re-create the VMRA HPTEs on the next KVM_RUN of any vcpu.)
    > > >
    > > > +4.76 KVM_IRQFD
    > > > +
    > > > +Capability: KVM_CAP_IRQFD
    > > > +Architectures: x86
    > > > +Type: vm ioctl
    > > > +Parameters: struct kvm_irqfd (in)
    > > > +Returns: 0 on success, -1 on error
    > > > +
    > > > +Allows setting an eventfd to directly trigger a guest interrupt
    > > > +kvm_irqfd.fd specifies the file descriptor to use as the eventfd and
    > > > +kvm_irqfd.gsi specifies the irqchip pin toggled by this event. By
    > > > +default this interface only supports edge triggered interrupts,
    > > > +meaning the specified gsi is asserted and immediately de-asserted
    > > > +when the eventfd is triggered.
    > >
    > > That's a bit confusing. This assert/deassert only has effect for level.
    > > Do we or do we not want to maintain this assert/deassert behaviour
    > > for level irqfds? If yes we shouldn't say it's unsupported if
    > > no we should not document it.
    > >
    > > Gleb, Avi, any thoughts?
    >
    > AIUI the assert/deassert manages to work for level (I actually had vfio
    > injecting these for a while and it seemed to work), but I don't think it
    > was ever designed for level interrupts and attempting to do that is
    > unsupported. Thanks,
    >
    > Alex

    So don't document assert/deassert then.

    > > > Specifying KVM_IRQFD_FLAG_DEASSIGN
    > > > +removes the previously set irqfd matching both kvm_irqfd.fd and
    > > > +kvm_irqfd.gsi.
    > > > +
    > > >
    > > > 5. The kvm_run structure
    > > > ------------------------
    >
    >


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