Re: [Qemu-devel] [PATCH V2 04/11] virtio-ccw: introduce ccw specific queue limit

[Jason Wang]

On Thu, Feb 26, 2015 at 9:02 PM, Cornelia Huck 
<address@hidden> wrote:
> On Thu, 26 Feb 2015 15:04:39 +0800
> Jason Wang <address@hidden> wrote:
>
> >  Instead of depending on marco, using a bus specific limit.
> >  
> >  Cc: Alexander Graf <address@hidden>
> >  Cc: Cornelia Huck <address@hidden>
> >  Cc: Christian Borntraeger <address@hidden>
> >  Cc: Richard Henderson <address@hidden>
> >  Signed-off-by: Jason Wang <address@hidden>
> >  ---
> >   hw/s390x/s390-virtio-ccw.c |  7 +++++--
> >   hw/s390x/virtio-ccw.c      | 13 +++++++------
> >   include/hw/virtio/virtio.h |  1 +
> >   3 files changed, 13 insertions(+), 8 deletions(-)
> >  
> >  diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> >  index 71bafe0..6aeb815 100644
> >  --- a/hw/s390x/s390-virtio-ccw.c
> >  +++ b/hw/s390x/s390-virtio-ccw.c
> >  @@ -43,6 +43,7 @@ void io_subsystem_reset(void)
> >  
> >   static int virtio_ccw_hcall_notify(const uint64_t *args)
> >   {
> >  +    VirtIODevice *vdev;
> >       uint64_t subch_id = args[0];
> >       uint64_t queue = args[1];
> >       SubchDev *sch;
> >  @@ -55,10 +56,12 @@ static int virtio_ccw_hcall_notify(const 
> > uint64_t *args)
> >       if (!sch || !css_subch_visible(sch)) {
> >           return -EINVAL;
> >       }
> >  -    if (queue >= VIRTIO_PCI_QUEUE_MAX) {
> >  +
> >  +    vdev = virtio_ccw_get_vdev(sch);
> >  +    if (queue >= virtio_get_queue_max(vdev)) {
>
> But we already know we have a virtio_ccw device, right? So why not 
> just
> check against VIRTIO_CCW_QUEUE_MAX?

The problem is whether or not you want to increase the max queue for 
ccw. If yes, for migration compatibility, you could not just use a 
marco here since legacy machine type will also get increased. Something 
dynamically like this is need so the machine initialization code can 
change this limit. 
> >           return -EINVAL;
> >       }
> >  -    virtio_queue_notify(virtio_ccw_get_vdev(sch), queue);
> >  +    virtio_queue_notify(vdev, queue);
> >       return 0;
> >  
> >   }
>
> (...)
>
> >  diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >  index 9fe0d92..04ad532 100644
> >  --- a/include/hw/virtio/virtio.h
> >  +++ b/include/hw/virtio/virtio.h
> >  @@ -93,6 +93,7 @@ typedef struct VirtQueueElement
> >   } VirtQueueElement;
> >  
> >   #define VIRTIO_PCI_QUEUE_MAX 64
> >  +#define VIRTIO_CCW_QUEUE_MAX 64
>
> Does generic code need to know about the ccw limit?

Seems not, will move it to ccw file.
> >  
> >   #define VIRTIO_NO_VECTOR 0xffff
> >