* Daniel P. Berrange (berra...@redhat.com) wrote: > The Linux kernel will query the SCSI "Block device characteristics" > VPD to determine the rotations per minute of the disk. If this has > the value 1, it is taken to be an SSD and so Linux sets the > 'rotational' flag to 0 for the I/O queue and will stop using that > disk as a source of random entropy. Other operating systems may > also take into account rotation rate when setting up default > behaviour. > > Mgmt apps should be able to set the rotation rate for virtualized > block devices, based on characteristics of the host storage in use, > so that the guest OS gets sensible behaviour out of the box. This > patch thus adds a 'rotation-rate' parameter for 'scsi-hd' and > 'scsi-block' device types. For the latter, this parameter will be > ignored unless the host device has TYPE_DISK. > > Signed-off-by: Daniel P. Berrange <berra...@redhat.com> > --- > hw/scsi/scsi-disk.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c > index 6e841fb5ff..a518080e7d 100644 > --- a/hw/scsi/scsi-disk.c > +++ b/hw/scsi/scsi-disk.c > @@ -104,6 +104,14 @@ typedef struct SCSIDiskState > char *product; > bool tray_open; > bool tray_locked; > + /* > + * 0x0000 - rotation rate not reported > + * 0x0001 - non-rotating medium (SSD) > + * 0x0002-0x0400 - reserved > + * 0x0401-0xffe - rotations per minute > + * 0xffff - reserved > + */ > + uint16_t rotation_rate; > } SCSIDiskState; > > static bool scsi_handle_rw_error(SCSIDiskReq *r, int error, bool > acct_failed); > @@ -605,6 +613,7 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, > uint8_t *outbuf) > outbuf[buflen++] = 0x83; // device identification > if (s->qdev.type == TYPE_DISK) { > outbuf[buflen++] = 0xb0; // block limits > + outbuf[buflen++] = 0xb1; /* block device characteristics */ > outbuf[buflen++] = 0xb2; // thin provisioning > } > break; > @@ -747,6 +756,15 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, > uint8_t *outbuf) > outbuf[43] = max_io_sectors & 0xff; > break; > } > + case 0xb1: /* block device characteristics */ > + { > + buflen = 8; > + outbuf[4] = (s->rotation_rate >> 8) & 0xff; > + outbuf[5] = s->rotation_rate & 0xff; > + outbuf[6] = 0; > + outbuf[7] = 0; > + break; > + } > case 0xb2: /* thin provisioning */ > { > buflen = 8; > @@ -2911,6 +2929,7 @@ static Property scsi_hd_properties[] = { > DEFAULT_MAX_UNMAP_SIZE), > DEFINE_PROP_UINT64("max_io_size", SCSIDiskState, max_io_size, > DEFAULT_MAX_IO_SIZE), > + DEFINE_PROP_UINT16("rotation_rate", SCSIDiskState, rotation_rate, 0), > DEFINE_BLOCK_CHS_PROPERTIES(SCSIDiskState, qdev.conf), > DEFINE_PROP_END_OF_LIST(), > }; > @@ -2982,6 +3001,7 @@ static const TypeInfo scsi_cd_info = { > static Property scsi_block_properties[] = { > DEFINE_BLOCK_ERROR_PROPERTIES(SCSIDiskState, qdev.conf), \ > DEFINE_PROP_DRIVE("drive", SCSIDiskState, qdev.conf.blk), > + DEFINE_PROP_UINT16("rotation_rate", SCSIDiskState, rotation_rate, 0), > DEFINE_PROP_END_OF_LIST(), > };
Are you sure you want this as a property of SCSIDiskState etc rather than a property on the underlying drive? Then if virtio devices etc wanted to pick this up later they could without needing extra parameters. Dave > > -- > 2.13.5 > > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK