Re: [Qemu-devel] virtio block device and sysfs

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/06/2010 04:42 PM, Marc Haber wrote:
> Hi,
>
> I am looking to get in touch with somebody who knows more about the
> connection between host configuration, qemu, kvm, and the virtio block
> device driver guest side than I know.
>
> My goal is to have a possibility to give a "speaking" name to any
> block device handed into a guest instance by the host. That name
> should be visible inside the guest, just as a LV is visible with its
> name in the system running the LVM.
>
> For example I would like to say on the qemu or kvm command line
> '-drive file=some-file,label=some-label,if=virtio', and have the
> string "some-label" show up somewhere in /sys/block in the guest, much
> as /sys/block/sda/device/model shows the hardware vendor and type for
> a standard SATA disk. The guest could then handle the information
> passed into it by the host with udev rules, allowing fstab constructs
> like "mount /dev/virtio/block/by-label/some-label as /usr"
>    

You probably would just want to plumb ,serial=X into the virtio-blk 
config space and have the driver use it.  Then you can do 
/dev/block/by-id/XXXXX

John attempted this and it was reverted because the implementation 
exhausted the PCI config space.

Regards,

Anthony Liguori

> Since I don't have pretty much clue about kernel programming, I guess
> that one would need to have qemu/kvm support for the additional label
> to be passed to the emulated/virtualized guest, and a modification to
> the guest kernel virtio driver which needs to accept the information
> passed by the host and to generate the appropriate entry in /sys.
>
> Am I correct in my assumption? Can you say who I need to talk to to
> get advice about how to implement this (or to have it implemented, if
> it's easy enough)?
>
> Any hints will be appreciated.
>
> Greetings
> Marc
>
>