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Date: Tue, 28 Apr 2015 09:14:07 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V7 08/16] virtio: introduce bus specific
 queue limit
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To: Jason Wang <jasowang@redhat.com>
Cc: qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, Christian Borntraeger <borntraeger@de.ibm.com>, Cornelia Huck <cornelia.huck@de.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On Tue, Apr 28, 2015 at 02:13:20PM +0800, Jason Wang wrote:
> 
> 
> On Tue, Apr 28, 2015 at 1:13 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> >On Tue, Apr 28, 2015 at 11:14:04AM +0800, Jason Wang wrote:
> >>     On Mon, Apr 27, 2015 at 7:05 PM, Michael S. Tsirkin
> >><mst@redhat.com> wrote:
> >> >On Thu, Apr 23, 2015 at 02:21:41PM +0800, Jason Wang wrote:
> >> >> This patch introduces a bus specific queue limitation. It will be
> >> >> useful for increasing the limit for one of the bus without
> >>disturbing
> >> >> other buses.
> >> >> Cc: Michael S. Tsirkin <mst@redhat.com>
> >> >> Cc: Alexander Graf <agraf@suse.de>
> >> >> Cc: Richard Henderson <rth@twiddle.net>
> >> >> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> >> >> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> >> >> Cc: Paolo Bonzini <pbonzini@redhat.com>
> >> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >> >> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> >> >
> >> >Is this still needed if you drop the attempt to
> >> >keep the limit around for old machine types?
> >> If we agree to drop, we probably need transport specific macro.
> >
> >You mean just rename VIRTIO_PCI_QUEUE_MAX to VIRTIO_QUEUE_MAX?
> >Fine, why not.
> 
> I mean keeping VIRTIO_PCI_QUEUE_MAX for pci only and just increase pci
> limit. And introduce e.g VIRTIO_PCI_QUEUE_CCW for ccw and keep it as 64.
> Since to my understanding, it's not safe to increase the limit for all other
> transports which was pointed out by Cornelia in V1:
> http://permalink.gmane.org/gmane.comp.emulators.qemu/318245.

I think all you need is add a check to CCW_CMD_SET_IND:
limit to 64 for legacy interrupts only.

-- 
MST