[Qemu-devel] Re: [PATCHv2] Support for booting from virtio disks

[Gleb Natapov <gleb@redhat.com>]

On Mon, May 10, 2010 at 10:58:45AM -0500, Anthony Liguori wrote:
> On 05/10/2010 10:54 AM, Gleb Natapov wrote:
> >On Mon, May 10, 2010 at 10:48:42AM -0500, Anthony Liguori wrote:
> >>On 05/10/2010 03:11 AM, Gleb Natapov wrote:
> >>>This patch adds native support for booting from virtio disks to Seabios.
> >>>
> >>>Signed-off-by: Gleb Natapov<gleb@redhat.com>
> >>A related problem that I think we need to think about how we solve
> >>is indicating to Seabios which device we want to boot from
> >>
> >>With your patch, a user can select a virtio device explicitly or if
> >>they use only one virtio device, it will Just Work.
> >>
> >>However, if a user uses IDE and virtio, or a user has multiple
> >>disks, they cannot select a device via -boot.
> >>
> >Isn't this problem unrelated to this patch?  I mean if I start qemu with
> >two ide devices can I specify from qemu command line which one I want to
> >boot from?
> 
> That's sort of what I'm asking.  If you compare this approach to
> extboot, extboot provided a capability to select a disk.  I think it
> can be argued though that this isn't a necessary feature to carry
> over and I'm looking for additional opinions on that.
> 
Well, extboot is just a hack and shouldn't be used with ide disks at
all. With extboot it is not possible to switch to another disk from
F12 menu for instance (is it actually possible to read more then one
disks with bios int13 when extboot is in use?). About specifying boot
disk from qemu command like I think it will be very useful. It is not
clear how to pass default boot device into Seabios though. We should
pass a bus boot device is attached too (ide/virtio) and an unique id
of the device on the bus.

--
			Gleb.