On Mon, 07/28 17:08, Paolo Bonzini wrote: > Right now scsi-generic is parsing the CDB, in order to compute > the expected number of bytes to be transferred. This is necessary > if DMA is done by the HBA via scsi_req_data, but it prevents executing > vendor-specific commands via scsi-generic because we don't know how > to parse them. > > If DMA is delegated to the SCSI layer via get_sg_list, we know in > advance how many bytes the guest will want to receive and we can pass > the information straight from the guest to SG_IO. In this case, it is > unnecessary to parse the CDB to get the same information. scsi-disk needs > it to detect underruns and overruns, but scsi-generic and scsi-block can > just ask the HBA about the transfer direction and size. > > This series introduces a new parse_cdb callback in both the device and > the HBA. The latter is called by scsi_bus_parse_cdb, which devices can > call for passthrough requests in their implementation of parse_cdb. > > Paolo > > v1->v2: use the "right" CDB size for non-vendor-specific commands, > as some drivers and/or firmware expect that and complain > if you pass a READ(10) command in a 16-byte CDB. Interdiff > here.
More learning than reviewing for me, so take this with a grain of salt: Reviewed-by: Fam Zheng <f...@redhat.com>
