Christian Borntraeger <borntrae...@de.ibm.com> writes: > Am 07.11.2014 10:17, schrieb Markus Armbruster: >> Christian Borntraeger <borntrae...@de.ibm.com> writes: [...] >>> Now here comes my proposal: >>> Markus statement brought up an idea of special casing DASDs support. We can >>> call an ioctl BIODASDINFO on the block device that will only >>> succeed if the host >>> disk is really a dasd. We could enable the auto detection for that case. >> >> If BIODASDINFO succeeds, QEMU uses that instead of making up device >> geometry as described above. Correct? >> >> Let's spell out when exactly BIODASDINFO succeeds, to avoid >> misunderstandings. It does when the backend is a DASD (/dev/dasd*). >> What about a partition on a DASD? A file in a filesystem on a DASD? > > BIODASDINFO (we will propbably use BIODASDINFO2) will succeed only if > the backend is backed by a dasd or its partitions. It will fail on > other block devices and files on a dasd. > > Now: when passing in only a dasd partition we cannot do any sane thing > with the dasd oddities inside the guest (e.g. creating dasd > partitions, reading volume label or TOC etc.) > So there is no need passing in geometry and block size. We could make > the special case even stricter and check for start == 0 when doing the > HDIO_GETGEO. > So pass-through of geometry and block size is only performed if > BIODASDINFO2 succeeds, and the GETGEO call indicates that this is not > a partions by having start == 0. > > Makes sense?
Yes. Thank you! [...]
