Michael S. Tsirkin wrote:
> Here's an untested patch with partial support for level triggered
> interrupts in irqfd. What this patch has: support for clearing interrupt
> on ack. What this patch does not have: support signalling eventfd on ack
> so that userspace can take action and e.g. reenable interrupt.
>
> Gleb, Marcelo, I'd like your input on the approach taken wrt locking.
> Does it look sane?
>
> Avi, how's the interface? I intend to also add an eventfd probably in
> the padding in the irqfd struct.
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Patch seems reasonable to me.
Acked-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
>
> ---
>
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index 230a91a..8bf16af 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -488,6 +488,7 @@ struct kvm_x86_mce {
> #endif
>
> #define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
> +#define KVM_IRQFD_FLAG_LEVEL (1 << 1)
>
> struct kvm_irqfd {
> __u32 fd;
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index 99017e8..fcbf5b5 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -45,12 +45,14 @@ struct _irqfd {
> struct kvm *kvm;
> struct eventfd_ctx *eventfd;
> int gsi;
> + int is_level;
> struct list_head list;
> poll_table pt;
> wait_queue_head_t *wqh;
> wait_queue_t wait;
> struct work_struct inject;
> struct work_struct shutdown;
> + struct kvm_irq_ack_notifier kian;
> };
>
> static struct workqueue_struct *irqfd_cleanup_wq;
> @@ -63,10 +65,15 @@ irqfd_inject(struct work_struct *work)
>
> mutex_lock(&kvm->irq_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);
> + if (!irqfd->is_level)
> + kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
> mutex_unlock(&kvm->irq_lock);
> }
>
> +static void irqfd_irq_acked(struct kvm_irq_ack_notifier *kian)
> +{
> + kvm_set_irq(kian->kvm, KVM_USERSPACE_IRQ_SOURCE_ID, kian->gsi, 0);
> +}
> /*
> * Race-free decouple logic (ordering is critical)
> */
> @@ -87,6 +94,9 @@ irqfd_shutdown(struct work_struct *work)
> */
> flush_work(&irqfd->inject);
>
> + if (irqfd->is_level)
> + kvm_unregister_irq_ack_notifier(&irqfd->kian);
> +
> /*
> * It is now safe to release the object's resources
> */
> @@ -166,7 +176,7 @@ irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
> }
>
> static int
> -kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
> +kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi, int is_level)
> {
> struct _irqfd *irqfd;
> struct file *file = NULL;
> @@ -180,6 +190,7 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
>
> irqfd->kvm = kvm;
> irqfd->gsi = gsi;
> + irqfd->is_level = is_level;
> INIT_LIST_HEAD(&irqfd->list);
> INIT_WORK(&irqfd->inject, irqfd_inject);
> INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
> @@ -198,6 +209,12 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
>
> irqfd->eventfd = eventfd;
>
> + if (is_level) {
> + irqfd->kian.gsi = gsi;
> + irqfd->kian.irq_acked = irqfd_irq_acked;
> + kvm_register_irq_ack_notifier(&irqfd->kian);
> + }
> +
> /*
> * Install our own custom wake-up handling so we are notified via
> * a callback whenever someone signals the underlying eventfd
> @@ -281,10 +298,13 @@ kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi)
> int
> kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
> {
> + if (flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_LEVEL))
> + return -EINVAL;
> +
> if (flags & KVM_IRQFD_FLAG_DEASSIGN)
> return kvm_irqfd_deassign(kvm, fd, gsi);
>
> - return kvm_irqfd_assign(kvm, fd, gsi);
> + return kvm_irqfd_assign(kvm, fd, gsi, !!(flags & KVM_IRQFD_FLAG_LEVEL));
> }
>
> /*
> --
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