Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation

[Paolo Bonzini]

Il 02/05/2012 12:18, Christian Borntraeger ha scritto:
> Maybe that really points to the problem that we are trying to solve here.
> For a dasd device, there is usually a 4096 byte block size and on the host
> these 4096 arereported via getss and getpbsz. 
> The geometry reported by the device driver is usually 15 head and 12 sectors
> per track, but actually means 12 sectors of 4096 bytes size (a track ~ 48k).
> 
> What I want to achieve is that the guest view is identical to the host view
> for cyls, heads, secs, and all block sizes.

I think what you want is _not_ to have the same view as the host.  What
you want is simply to have a default that is consistent with what is
common on actual s390 disks.

Perhaps what we want here is to move the guessing of cyls/head/sector
count from -drive to -device, so that virtio-blk-s390 can apply a
different default (cyls=auto, head=15, sector=12, and also lbsz=pbsz=4096).

Markus, have you ever thought about that?  I'm a bit torn because these
are media parameters rather than device parameters, on the other hand
the same applies to lbsz/pbsz at least.

Paolo