Re: Xen and LVM backed domu's

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

On Thursday 25 February 2010 14:17:46 haad wrote:
> > I recently found out that HVM domUs running with lvm-backed storage
> > detect a 0MB hard disk - this is not a domU-OS specific problem, as qemu
> > itself reports 0MB
> > in the "bios" - thus making them unusable.
> >
> > Not sure where the problem might be here, but I suspect qemu. Xen, as I
> > recall, (I don't have my NetBSD/Xen box nearby) correctly detects the
> > size of the logical volume.
>
> Hmm yes that can be easily problem if Xen qemu uses some different
> disk ioctls which are not supported by dm driver.
>
> I think that ideal would be change disk_ioctl[1] routine to work with
> more that one IOCTL and listen for all other different disk size
> ioctls calls. disk_ioctl can use dictionary to create every possible
> structure for caller.

This problem is not specific to LVM. You can reproduce this when you tell Xen
to use a physical disk in general for the domU.


> Please make a PR for this issue because otherwise it can be lost.
> Because I'm little bit busy these
> days with ZFS.
>
> [1] http://nxr.netbsd.org/xref/src/sys/kern/subr_disk.c#487