On 07/15/2015 05:11 PM, Cornelia Huck wrote: > On Wed, 15 Jul 2015 13:29:56 +0800 > Jason Wang <jasow...@redhat.com> wrote: > >> Hi all: >> >> This series tries to set feature correctly for virtio-blk when virtio >> 1.0 is supported. Two isssues were addressed according to the spec: >> >> - scsi passthrough was not support in 1.0. This is done by, 1) disable >> scsi by defautl for 2.4 machine type and fail the initialization >> when both scsi and 1.0 were set. >> - any layout must be set for transitional device. This is done by set >> any layout when 1.0 is supported. >> >> Please review >> >> Changes from V1: >> - Split virtio-net changes out of the series >> - Enable VIRTIO_BLK_F_SCSI only when scsi is set >> - Disable scsi by default and compat it for legacy machine types >> - Let get_features() can fail and fail the initialization of >> virito-blk when both 1.0 and scsi were supported. > Hm, this seems confusing to me mainly due to the different way > transitional devices are handled by pci and ccw. > > For virtio-pci: (please correct me if I misunderstood) > - devices (except input) are transitional by default > - user can disable legacy or modern support > - drivers can use method they prefer, depending on VERSION_1 > > For virtio-ccw: > - transitional means "in limbo" regarding legacy or modern > - devices become legacy if features are read without negotiation of a > revision, or if revision 0 is negotiated > - they become modern if revision 1 is negotiated > > That implies that for ccw, a transitional device does not offer any > features: It either transitions to the legacy or modern state if a > revision was negotiated, or it becomes a legacy device by reading > features (which are the legacy features, then). While pci has "real" > transitional devices needing to offer a certain feature set. > > I'm not sure what the solution is here: basically, ccw needs a dynamic > feature set, while pci does not. >
So, if I understand correctly. All virtio-ccw devices are transitional since user can disable neither legacy nor modern. It looks to me then we can set VIRTIO_F_VERSION_1 unconditionally for ccw. Then there's no issue left?
