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

[Jason Wang <jasowang@redhat.com>]

On Thu, Feb 26, 2015 at 9:02 PM, Cornelia Huck 
<cornelia.huck@de.ibm.com> wrote:
> On Thu, 26 Feb 2015 15:04:39 +0800
> Jason Wang <jasowang@redhat.com> wrote:
> 
>>  Instead of depending on marco, using a bus specific limit.
>>  
>>  Cc: Alexander Graf <agraf@suse.de>
>>  Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
>>  Cc: Christian Borntraeger <borntraeger@de.ibm.com>
>>  Cc: Richard Henderson <rth@twiddle.net>
>>  Signed-off-by: Jason Wang <jasowang@redhat.com>
>>  ---
>>   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
>>  
>