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Date: Tue, 28 Jul 2015 10:57:27 +0800
From: Jason Wang <jasowang@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: "Michael S. Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
Cc: cornelia.huck@de.ibm.com, qemu-devel@nongnu.org



On 07/27/2015 07:26 PM, Michael S. Tsirkin wrote:
> 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?

I've considered this, but a little problem is 'disable-modern' only
works for pci.

>> 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);
>>> +    }