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    SubjectRe: [KVM PATCH v3 2/2] kvm: add support for irqfd via eventfd-notification interface
    On Mon, Apr 27, 2009 at 02:33:34PM -0400, Gregory Haskins wrote:
    > This allows an eventfd to be registered as an irq source with a guest. Any
    > signaling operation on the eventfd (via userspace or kernel) will inject
    > the registered GSI at the next available window.
    > Signed-off-by: Gregory Haskins <>

    If we ever want to use this with e.g. MSI-X emulation in guest, and want
    to be stricly compliant to MSI-X, we'll need a way for guest to mask
    interrupts, and for host to report that a masked interrupt is pending.
    Ideally, all this will be doable with a couple of mmapped pages to avoid
    vmexits/system calls.

    > +static void
    > +irqfd_inject(struct work_struct *work)
    > +{
    > + struct _irqfd *irqfd = container_of(work, struct _irqfd, work);
    > + struct kvm *kvm = irqfd->kvm;
    > +
    > + mutex_lock(&kvm->lock);
    > + kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
    > + kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
    > + mutex_unlock(&kvm->lock);

    This will do weird stuff (deliver the irq twice) if the irq is
    MSI/MSI-X. I know this was discussed already and is a temporary
    shortcut, but maybe add a comment that we really want kvm_toggle_irq,
    so that we won't forget?

    > +}
    > +


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