virtio with 2.6.25-rc8: problem with /dev/vda

virtio with 2.6.25-rc8: problem with /dev/vda

[Jun Koi]

Hi,

I am trying virtio: guest is running 2.6.25-rc8 kernel, with virtio
compiled in. In Grub menu, I changed

"root=/dev/sda1"

to:

"root=/dev/vda1".

(That is guided by http://kvm.qumranet.com/kvmwiki/Virtio)

However, I got booting error like "/dev/vda1 doest exist...", so boot
failure. How can I fix this?

Thanks,
Jun

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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Felix Leimbach]

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>  However, I got booting error like "/dev/vda1 doest exist...", so boot
>  failure. How can I fix this?

make sure that your command line on the host looks like that:
kvm -drive file=<your-image>,if=virtio,boot=on <other stuff here>

And check that the guest has the following kernel option enabled:
CONFIG_VIRTIO_BLK

regards,
Felix

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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Jun Koi]

On 4/9/08, Felix Leimbach <felix.leimbach@gmx.net> wrote:
>
>  > However, I got booting error like "/dev/vda1 doest exist...", so boot
>  > failure. How can I fix this?
>
>  make sure that your command line on the host looks like that:
>  kvm -drive file=<your-image>,if=virtio,boot=on <other
> stuff here>
>
>  And check that the guest has the following kernel option enabled:
>  CONFIG_VIRTIO_BLK

Yes, I missed this VIRTIO_BLK!

It might be easier if we put all of virtio stuffs under the same menu,
so nobody can miss anything?

Thanks,
Jun

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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Anthony Liguori]

Jun Koi wrote:
> On 4/9/08, Felix Leimbach <felix.leimbach@gmx.net> wrote:
>   
>>  > However, I got booting error like "/dev/vda1 doest exist...", so boot
>>  > failure. How can I fix this?
>>
>>  make sure that your command line on the host looks like that:
>>  kvm -drive file=<your-image>,if=virtio,boot=on <other
>> stuff here>
>>
>>  And check that the guest has the following kernel option enabled:
>>  CONFIG_VIRTIO_BLK
>>     
>
> Yes, I missed this VIRTIO_BLK!
>
> It might be easier if we put all of virtio stuffs under the same menu,
> so nobody can miss anything?
>   

As distros upgrade their kernels to 2.6.25 and greater, it'll all get 
built by default so users won't have to deal with this sort of thing.

Regards,

Anthony Liguori

> Thanks,
> Jun
>
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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Jun Koi]

On 4/10/08, Anthony Liguori <anthony@codemonkey.ws> wrote:
> Jun Koi wrote:
>
> > On 4/9/08, Felix Leimbach <felix.leimbach@gmx.net> wrote:
> >
> >
> > >  > However, I got booting error like "/dev/vda1 doest exist...", so boot
> > >  > failure. How can I fix this?
> > >
> > >  make sure that your command line on the host looks like that:
> > >  kvm -drive file=<your-image>,if=virtio,boot=on <other
> > > stuff here>
> > >
> > >  And check that the guest has the following kernel option enabled:
> > >  CONFIG_VIRTIO_BLK
> > >
> > >
> >
> > Yes, I missed this VIRTIO_BLK!
> >
> > It might be easier if we put all of virtio stuffs under the same menu,
> > so nobody can miss anything?
> >
> >
>
>  As distros upgrade their kernels to 2.6.25 and greater, it'll all get built
> by default so users won't have to deal with this sort of thing.

Thanks.

Now I succesfully installed 2.6.25-rc8, and virtio block device works
well. But from inside my VM, how can I say it is using virtio for
block?

And is there any number about the performance gain using virtio block?

Another question: currently I have some problem with network: I use option

"-net nic,model=virtio"

and try to configure VM from inside after booting, network doesnt
work, even after I manually configure eth0.

How to fix that network problem?

Thanks,
Jun

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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Jorge Lucángeli Obes]

On Thu, Apr 10, 2008 at 12:59 AM, Jun Koi <junkoi2004@gmail.com> wrote:
>  Now I succesfully installed 2.6.25-rc8, and virtio block device works
>  well. But from inside my VM, how can I say it is using virtio for
>  block?
>
>  And is there any number about the performance gain using virtio block?
>
>  Another question: currently I have some problem with network: I use option
>
>  "-net nic,model=virtio"
>
>  and try to configure VM from inside after booting, network doesnt
>  work, even after I manually configure eth0.
>
>  How to fix that network problem?

'-net nic,...' only specifies the "hardware" part of QEMU/KVM's
networking. You also need to specify whether you are going to use
usermode networking or bridged networking. QEMU documentation covers
both modes pretty well.

To test the card quickly, use usermode networking, where QEMU provides
a usermode network stack (complete with DHCP server) that let's you
use the VM as if it were behind a completely restrictive firewall that
only allows outbound connections.

'-net nic,model=virtio -net user'

It's a great way to test the network card. If your host has an
Internet connection, firing up a browser in the guest (after getting
the guest interface up using DHCP) and accessing a web page should
"just work".

Cheers!
Jorge

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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Jun Koi]

On 4/10/08, Jorge Lucángeli Obes <t4m5yn@gmail.com> wrote:
> On Thu, Apr 10, 2008 at 12:59 AM, Jun Koi <junkoi2004@gmail.com> wrote:
>  >  Now I succesfully installed 2.6.25-rc8, and virtio block device works
>  >  well. But from inside my VM, how can I say it is using virtio for
>  >  block?
>  >
>  >  And is there any number about the performance gain using virtio block?
>  >
>  >  Another question: currently I have some problem with network: I use option
>  >
>  >  "-net nic,model=virtio"
>  >
>  >  and try to configure VM from inside after booting, network doesnt
>  >  work, even after I manually configure eth0.
>  >
>  >  How to fix that network problem?
>
>
> '-net nic,...' only specifies the "hardware" part of QEMU/KVM's
>  networking. You also need to specify whether you are going to use
>  usermode networking or bridged networking. QEMU documentation covers
>  both modes pretty well.
>
>  To test the card quickly, use usermode networking, where QEMU provides
>  a usermode network stack (complete with DHCP server) that let's you
>  use the VM as if it were behind a completely restrictive firewall that
>  only allows outbound connections.
>
>  '-net nic,model=virtio -net user'
>
>  It's a great way to test the network card. If your host has an
>  Internet connection, firing up a browser in the guest (after getting
>  the guest interface up using DHCP) and accessing a web page should
>  "just work".

"-net user" works, thanks!

I didnt use the option because I think that is default. But it seems
if you use "-net" (for "model=virtio" in this case), you must specify
the networking mode.

Regards,
Jun

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Re: virtio with 2.6.25-rc8: problem with /dev/vda

[Dor Laor]

On Thu, 2008-04-10 at 14:14 +0900, Jun Koi wrote:
> On 4/10/08, Jorge Lucángeli Obes <t4m5yn@gmail.com> wrote:
> > On Thu, Apr 10, 2008 at 12:59 AM, Jun Koi <junkoi2004@gmail.com> wrote:
> >  >  Now I succesfully installed 2.6.25-rc8, and virtio block device works
> >  >  well. But from inside my VM, how can I say it is using virtio for
> >  >  block?
> >  >
> >  >  And is there any number about the performance gain using virtio block?
> >  >
> >  >  Another question: currently I have some problem with network: I use option
> >  >
> >  >  "-net nic,model=virtio"
> >  >
> >  >  and try to configure VM from inside after booting, network doesnt
> >  >  work, even after I manually configure eth0.
> >  >
> >  >  How to fix that network problem?
> >
> >
> > '-net nic,...' only specifies the "hardware" part of QEMU/KVM's
> >  networking. You also need to specify whether you are going to use
> >  usermode networking or bridged networking. QEMU documentation covers
> >  both modes pretty well.
> >
> >  To test the card quickly, use usermode networking, where QEMU provides
> >  a usermode network stack (complete with DHCP server) that let's you
> >  use the VM as if it were behind a completely restrictive firewall that
> >  only allows outbound connections.
> >
> >  '-net nic,model=virtio -net user'
> >
> >  It's a great way to test the network card. If your host has an
> >  Internet connection, firing up a browser in the guest (after getting
> >  the guest interface up using DHCP) and accessing a web page should
> >  "just work".
> 
> "-net user" works, thanks!
> 

For general knowledge -net tap drastically improves performance.
There is also work in progress mainly by Rusty to do copy-less tap
networking.

> I didnt use the option because I think that is default. But it seems
> if you use "-net" (for "model=virtio" in this case), you must specify
> the networking mode.
> 
> Regards,
> Jun
> 
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