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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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