The "Block Limits" Inquiry VPD page is optional for any SCSI device,
but if it's supported it provides a hint of the maximum I/O transfer
length for this particular device. If this page is supported by the
disk, let's issue that Inquiry and use the minimum of it and the
SCSI controller limit. That will cover this scenario:
qemu-system-s390x ...
-device virtio-scsi-ccw,id=scsi0,max_sectors=32768 ...
-drive file=/dev/sda,if=none,id=drive0,format=raw ...
-device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,
drive=drive0,id=disk0,max_io_size=1048576
controller: 32768 sectors x 512 bytes/sector = 16777216 bytes
disk: 1048576 bytes
Now that we have a limit for a virtio-scsi disk, compare that with the
limit for the virtio-scsi controller when we actually build the I/O.
The minimum of these two limits should be the one we use.
Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170510155359.32727-7-farman@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
The "Supported Pages" Inquiry EVPD page is mandatory for all SCSI devices,
and is used as a gateway for what VPD pages the device actually supports.
Let's issue this Inquiry, and dump that list with the debug facility.
Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170510155359.32727-6-farman@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
If we want to issue any of the SCSI Inquiry EVPD pages,
which we do, we could use this function to issue both types
of commands with a little bit of refactoring.
Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170510155359.32727-5-farman@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
