virtio block drivers not working

virtio block drivers not working

[Caleb Tennis]

I've been very unsuccessful in using the virtio block drivers inside  
of a guest.  I can't seem to make them active.  I'm positive my kernel  
has support for them turned on (not as a module, but as a direct built  
in), but when I change one of my ide drives over to virtio and boot,  
it isn't found, and nothing under /sys or /dev indicates the presence  
of a device.  dmesg doesn't indicate anything about them either.  I DO  
have virtio networking enabled and working, so I know as a whole that  
some of the virtio subsystem is functional.

The only thing I think I'm doing possibly differently than normal is  
using the "-kernel" option to boot up from a kernel image vs. having  
an installed boot image via lilo or grub.  Would this make any  
difference?

Is there any way for me to debug some more as to why the block drivers  
don't seem to be showing up?

Thanks,
Caleb

Re: virtio block drivers not working

[Tomasz Chmielewski]

Caleb Tennis schrieb:
> I've been very unsuccessful in using the virtio block drivers inside of 
> a guest.  I can't seem to make them active.  I'm positive my kernel has 
> support for them turned on (not as a module, but as a direct built in), 
> but when I change one of my ide drives over to virtio and boot, it isn't 
> found, and nothing under /sys or /dev indicates the presence of a 
> device.  dmesg doesn't indicate anything about them either.  I DO have 
> virtio networking enabled and working, so I know as a whole that some of 
> the virtio subsystem is functional.
> 
> The only thing I think I'm doing possibly differently than normal is 
> using the "-kernel" option to boot up from a kernel image vs. having an 
> installed boot image via lilo or grub.  Would this make any difference?
> 
> Is there any way for me to debug some more as to why the block drivers 
> don't seem to be showing up?

Did you try other guests?

For example, try downloading a SystemRescueCd beta - it includes virtio 
drivers:

http://www.sysresccd.org/Beta-x86

Boot the guest from this CD, with a drive attached as virtio.

Load virtio drivers - do you see /dev/vda?


-- 
Tomasz Chmielewski
http://wpkg.org

Re: virtio block drivers not working

[Caleb Tennis]

On Mar 22, 2009, at 2:34 PM, Tomasz Chmielewski wrote:

> Did you try other guests?
>
> For example, try downloading a SystemRescueCd beta - it includes  
> virtio drivers:
>
> http://www.sysresccd.org/Beta-x86
>
> Boot the guest from this CD, with a drive attached as virtio.

Ok, booted.

>
> Load virtio drivers - do you see /dev/vda?
>

Yes, I do.  I suppose this tells me there's a problem in my kernel,  
but I guess I'm not sure what else to enable to get virtio working in  
my normal boot kernel.

Thanks,
Caleb

Re: virtio block drivers not working

[Christoph Hellwig]

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?

Re: virtio block drivers not working

[Caleb Tennis]

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

Re: virtio block drivers not working

[Markus Armbruster]

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.