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Date: Mon, 27 Jul 2015 14:26:03 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V4 2/3] virtio-blk: fail get_features when
 both scsi and 1.0 were set
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: cornelia.huck@de.ibm.com, Jason Wang <jasowang@redhat.com>, qemu-devel@nongnu.org

On Mon, Jul 27, 2015 at 12:28:23PM +0200, Paolo Bonzini wrote:
> 
> 
> On 27/07/2015 11:49, Jason Wang wrote:
> > +    if (__virtio_has_feature(features, VIRTIO_F_VERSION_1)) {
> 
> No double underscores in userspace code.  Longstanding so it can be
> fixed after 2.4 is out---but please remember to do it.
> 
> > +        if (s->conf.scsi) {
> > +            error_setg(errp, "Virtio 1.0 does not support scsi passthrough!");
> 
> Unclear error message, as one would expect SCSI passthrough not to work
> anyway for e.g. a disk backed by a file.

Right - so I suggested:
	Virtio modern does not support scsi passthrough - please set disable-modern=on or switch to virtio-scsi.
With that change - ACK?

> 
> It's not a big deal as long as you will disable VIRTIO_BLK_F_SCSI by
> default in the same release that enables VIRTIO_F_VERSION_1 by default.
> 
> Paolo
> > +            return 0;
> > +        }
> > +        virtio_add_feature(&features, VIRTIO_F_ANY_LAYOUT);
> > +    } else {
> > +        virtio_add_feature(&features, VIRTIO_BLK_F_SCSI);
> > +    }