Gregory Haskins wrote:
> 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>
Actually, one thing I didn't think of earlier is whether a
CAP_IRQFD_LEVEL kind of feature is required. I would think not, since
the baseline IRQFD hasnt been officially published yet.
But its something to consider.
-Greg
>
>> ---
>>
>> 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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>
>
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