On Wed, 22 Jul 2015 17:35:07 +0800 Jason Wang <jasow...@redhat.com> wrote:
> > > On 07/22/2015 04:58 PM, Cornelia Huck wrote: > > On Wed, 22 Jul 2015 13:59:51 +0800 > > Jason Wang <jasow...@redhat.com> 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 <jasow...@redhat.com> > >> --- > >> 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. > > I don't see much difference. Both of our patches needs to set scsi to > off to have 1.0 device. And I don't see advantages that did it from > transport. If it has, we probably need something similar in virtio-pci. The crux of the problem seems to be that pci and ccw have different approaches on supporting legacy and modern devices... > > > > > 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 > > > > Looks like patch "virtio-blk: scsi is legacy only" breaks backward > compatibility because VIRTIO_BLK_F_SCSI was not notified when scsi is off. Yeah, that's what I feared.