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Date: Wed, 15 Jul 2015 16:31:44 +0800
From: Jason Wang <jasowang@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V2 2/5] virtio-blk: advertise scsi only
	when scsi is set
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To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, cornelia.huck@de.ibm.com, qemu-block@nongnu.org, stefanha@redhat.com, mst@redhat.com



On 07/15/2015 03:57 PM, Paolo Bonzini wrote:
>
> On 15/07/2015 07:29, Jason Wang wrote:
>> Cc: Stefan Hajnoczi <stefanha@redhat.com>
>> Cc: Kevin Wolf <kwolf@redhat.com>
>> Cc: qemu-block@nongnu.org
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>  hw/block/virtio-blk.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
>> index 4c27974..761d763 100644
>> --- a/hw/block/virtio-blk.c
>> +++ b/hw/block/virtio-blk.c
>> @@ -731,7 +731,9 @@ static uint64_t virtio_blk_get_features(VirtIODevice *vdev, uint64_t features,
>>      virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
>>      virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
>>      virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
>> -    virtio_add_feature(&features, VIRTIO_BLK_F_SCSI);
>> +    if (s->conf.scsi) {
>> +        virtio_add_feature(&features, VIRTIO_BLK_F_SCSI);
>> +    }
> This must only be done for newer machine types only, or you change guest
> ABI for scsi=off.  Effectively you have to split it in two properties,
> "scsi" and "always_set_f_scsi".
>
> Paolo

And always_set_f_scsi is true only for legacy machine types?