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    SubjectRe: [PATCH 3/4] kvm: Extend irqfd to support level interrupts
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    On Sun, 2012-06-24 at 11:28 +0300, Michael S. Tsirkin wrote:
    > On Fri, Jun 22, 2012 at 04:16:17PM -0600, Alex Williamson wrote:
    > > diff --git a/include/linux/kvm.h b/include/linux/kvm.h
    > > index 2ce09aa..a916186 100644
    > > --- a/include/linux/kvm.h
    > > +++ b/include/linux/kvm.h
    > > @@ -618,6 +618,7 @@ struct kvm_ppc_smmu_info {
    > > #define KVM_CAP_PPC_GET_SMMU_INFO 78
    > > #define KVM_CAP_S390_COW 79
    > > #define KVM_CAP_PPC_ALLOC_HTAB 80
    > > +#define KVM_CAP_IRQFD_LEVEL_EOI 81
    > >
    > > #ifdef KVM_CAP_IRQ_ROUTING
    > >
    > > @@ -683,12 +684,15 @@ struct kvm_xen_hvm_config {
    > > #endif
    > >
    > > #define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
    > > +/* Available with KVM_CAP_IRQFD_LEVEL_EOI */
    > > +#define KVM_IRQFD_FLAG_LEVEL_EOI (1 << 1)
    > >
    > > struct kvm_irqfd {
    > > __u32 fd;
    > > __u32 gsi;
    > > __u32 flags;
    > > - __u8 pad[20];
    > > + __u32 fd2;
    > > + __u8 pad[16];
    > > };
    > >
    > > struct kvm_clock_data {
    > > diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
    > > index c307c24..2bc7275 100644
    > > --- a/virt/kvm/eventfd.c
    > > +++ b/virt/kvm/eventfd.c
    > > @@ -49,9 +49,13 @@ struct _irqfd {
    > > wait_queue_t wait;
    > > /* Update side is protected by irqfds.lock */
    > > struct kvm_kernel_irq_routing_entry __rcu *irq_entry;
    > > - /* Used for level IRQ fast-path */
    > > + /* Used for IRQ fast-path */
    > > int gsi;
    > > struct work_struct inject;
    > > + /* Used for level EOI path */
    > > + int irq_source_id;
    > > + struct eventfd_ctx *eoi_eventfd;
    > > + struct kvm_irq_ack_notifier notifier;
    > > /* Used for setup/shutdown */
    > > struct eventfd_ctx *eventfd;
    > > struct list_head list;
    > > @@ -62,7 +66,7 @@ struct _irqfd {
    > > static struct workqueue_struct *irqfd_cleanup_wq;
    > >
    > > static void
    > > -irqfd_inject(struct work_struct *work)
    > > +irqfd_inject_edge(struct work_struct *work)
    > > {
    > > struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
    > > struct kvm *kvm = irqfd->kvm;
    > > @@ -71,6 +75,23 @@ irqfd_inject(struct work_struct *work)
    > > kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
    > > }
    > >
    > > +static void
    > > +irqfd_inject_level(struct work_struct *work)
    > > +{
    > > + struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
    > > +
    > > + kvm_set_irq(irqfd->kvm, irqfd->irq_source_id, irqfd->gsi, 1);
    > > +}
    > > +
    >
    > I think that we can actually do this for all interrupts
    > unconditionally. We used to need to clear level for edge, but nomore.
    > Once you do this, can't this patch be replaced with 4/4 completely?

    Nope, as described in my reply there, we can't mix IRQFD and IRQ_LINE
    for a level interrupt because we need a separate source id and have no
    way to specify it with IRQ_LINE. Thanks,

    Alex



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