qemu does not accept regular disk geometry

[Hadmut Danisch]

Hi,

I am currently hunting a strange bug in qemu/kvm:

I am using an lvm logical volume as a virtual hard disk for a virtual machine.

I use fdisk or parted to create a partition table and partitions, kpartx to generate the device entries for the partitions, then install linux on ext3/ext4 with grub or msdos filesystem with syslinux.

But then, in most cases even the boot process fails or behaves strangely, sometimes even mounting the file system in the virtual machine fails. It seems as if there is a problem with the virtual disk geometry. The problem does not seem to occur if I reboot the host system after creating the partition table on the logical volume. I guess the linux kernel needs to learn the disk geometry by reboot. A blkdev --rereadpt does not work on lvm volumes.

The first approach to test/fix the problem would be to pass the disk geometry to qemu/lvm with the -drive option. Unfortunately, qemu/kvm does not accept the default geometry with 255 heads and 63 sectors. Seems to limit the number of heads to 16, thus limiting the disk size.

[Hadmut Danisch (hadmut)]

Seems to be the same issue as in
http://qemu-forum.ipi.fi/viewtopic.php?f=4&t=5218

[Hadmut Danisch (hadmut)]

has been (orally) confirmed by other users.

It is effectively impossible to reliably install a system on an lvm logical device and run it under kvm/qemu

[Thomas Huth (th-huth)]

Which version of QEMU have you been using for your tests? Can you still reproduce this problem with the latest version of QEMU?

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]