[Qemu-devel] Re: [PATCH-RFC 03/13] virtio: add iofd/irqfd support

[Michael S. Tsirkin]

On Tue, Jan 12, 2010 at 04:36:45PM -0600, Anthony Liguori wrote:
> On 01/11/2010 11:17 AM, Michael S. Tsirkin wrote:
>> Add binding API to set iofd/irqfd support.
>> Will be used by vhost.
>>
>> Signed-off-by: Michael S. Tsirkin<address@hidden>
>> ---
>>   hw/virtio.c |   13 ++++++++++---
>>   hw/virtio.h |    4 ++++
>>   2 files changed, 14 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/virtio.c b/hw/virtio.c
>> index 8e3c9ad..b9ec863 100644
>> --- a/hw/virtio.c
>> +++ b/hw/virtio.c
>> @@ -572,6 +572,12 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int 
>> queue_size,
>>       return&vdev->vq[i];
>>   }
>>
>> +void virtio_irq(VirtIODevice *vdev, VirtQueue *vq)
>> +{
>> +    vdev->isr |= 0x01;
>> +    virtio_notify_vector(vdev, vq->vector);
>> +}
>> +
>>   void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
>>   {
>>       /* Make sure used ring is updated before we check NO_INTERRUPT. */
>> @@ -582,8 +588,7 @@ void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
>>            (vq->inuse || vring_avail_idx(vq) != vq->last_avail_idx)))
>>           return;
>>
>> -    vdev->isr |= 0x01;
>> -    virtio_notify_vector(vdev, vq->vector);
>> +    virtio_irq(vdev, vq);
>>   }
>>
>>   void virtio_notify_config(VirtIODevice *vdev)
>> @@ -696,8 +701,10 @@ VirtIODevice *virtio_common_init(const char *name, 
>> uint16_t device_id,
>>       vdev->queue_sel = 0;
>>       vdev->config_vector = VIRTIO_NO_VECTOR;
>>       vdev->vq = qemu_mallocz(sizeof(VirtQueue) * VIRTIO_PCI_QUEUE_MAX);
>> -    for(i = 0; i<  VIRTIO_PCI_QUEUE_MAX; i++)
>> +    for(i = 0; i<  VIRTIO_PCI_QUEUE_MAX; i++) {
>>           vdev->vq[i].vector = VIRTIO_NO_VECTOR;
>> +        vdev->vq[i].vdev = vdev;
>> +    }
>>
>>       vdev->name = name;
>>       vdev->config_len = config_size;
>> diff --git a/hw/virtio.h b/hw/virtio.h
>> index ca840e1..193b3f9 100644
>> --- a/hw/virtio.h
>> +++ b/hw/virtio.h
>> @@ -88,6 +88,8 @@ typedef struct {
>>       int (*load_config)(void * opaque, QEMUFile *f);
>>       int (*load_queue)(void * opaque, int n, QEMUFile *f);
>>       unsigned (*get_features)(void * opaque);
>> +    int (*set_irqfd)(void * opaque, int n, int fd, bool assigned);
>> +    int (*set_queuefd)(void * opaque, int n, int fd, bool assigned);
>>    
>
> I'd like to see us abstract things like irqfd a bit more.  It should be  
> a first class object with an method to raise/lower.  In fact, you can  
> probably just use qemu_irq.
>
> Regards,
>
> Anthony Liguori

With a single provider, I fail to see the point of extra abstraction
layers, and I have no idea how a good abstraction would look. Let's see
when we have multiple implementations, then we can abstract them as
appropriate.  Also, irqfd does not have methods to raise/lower so
qemu_irq is far from a good fit.

-- 
MST