Re: virtio block drivers not working

[Markus Armbruster <armbru@redhat.com>]

Caleb Tennis <caleb@aei-tech.com> writes:

> On Mar 22, 2009, at 5:30 PM, Christoph Hellwig wrote:
>
>> I do you virtio block in a very similar setup to yours (fully static
>> kernel, -kernel option to kvm/qemu) sucesfully for quite a a while.
>>
>> Can you post your kernel .config and the contents of /proc/devices
>> and /proc/partitions to debug this further?
>>
>
> I've found the problem.  In my testing, I was changing my second drive
> from ide to virtio, so it looked like this:
>
> -drive index=0,media=disk,if=ide,file=/root
> -drive index=1,media=disk,if=virtio,file=/data
>
> This doesn't work though, even as vdb, as since the interface is the
> first virtio, the index needs to be set back to 0.  This gives me a /
> dev/vda like I was expecting.
>
> Thanks,
> Caleb

Yes, the common loop to create virtio block devices (all three copies of
it) stops at the first unused unit number / index.  A rude trap for the
unwary.  The device configuration patch I'm working on upstream doesn't
do that.