Re: [Qemu-devel] [PATCH V3 2/3] virtio-blk: fail get_features when both scsi and 1.0 were set

[Cornelia Huck]

On Wed, 22 Jul 2015 13:59:51 +0800
Jason Wang <address@hidden> wrote:

> SCSI passthrough was no longer supported in virtio 1.0, so this patch
> fail the get_features() when both 1.0 and scsi is set. And also only
> advertise VIRTIO_BLK_F_SCSI for legacy virtio-blk device.
> 
> Signed-off-by: Jason Wang <address@hidden>
> ---
>  hw/block/virtio-blk.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 4c27974..4716c3e 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -731,7 +731,14 @@ 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 (__virtio_has_feature(features, VIRTIO_F_VERSION_1)) {
> +        if (s->conf.scsi) {
> +            error_setg(errp, "Virtio 1.0 does not support scsi 
> passthrough!");
> +            return 0;
> +        }
> +    } else {
> +        virtio_add_feature(&features, VIRTIO_BLK_F_SCSI);
> +    }
> 
>      if (s->conf.config_wce) {
>          virtio_add_feature(&features, VIRTIO_BLK_F_CONFIG_WCE);

Do we advertise F_SCSI even if scsi is not configured in order to keep
the same bits as before? I'm afraid I don't remember, that thread was
long :/

I'm asking because I'd like to depend on that bit to decide whether I
can negotiate revision 1 for ccw and subsequently offer VERSION_1. It
would be an easy thing to do, and I'd like to avoid mucking around with
device-specific configuration from the transport.

To illustrate what I'm talking about, my current patchset for virtio-1
on ccw is here:

git://github.com/cohuck/qemu virtio-1-ccw-2.5