Re: [Qemu-devel] Boot order problem and disable iPXE/gPXE

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jan 05, 2012 at 10:27:44AM +0100, Gerhard Wiesinger wrote:
> On Thu, 5 Jan 2012, Gleb Natapov wrote:
> 
> >On Thu, Jan 05, 2012 at 10:09:44AM +0100, Gerhard Wiesinger wrote:
> >>On Thu, 5 Jan 2012, Gleb Natapov wrote:
> >>
> >>>On Thu, Jan 05, 2012 at 09:23:02AM +0100, Gerhard Wiesinger wrote:
> >>>>On Thu, 5 Jan 2012, Gerd Hoffmann wrote:
> >>>>
> >>>>>On 01/04/12 19:02, Gerhard Wiesinger wrote:
> >>>>>>Hello,
> >>>>>>
> >>>>>>I'm having the following boot order problem using an SCSI option ROM:
> >>>>>>
> >>>>>
> >>>>>>Still boots the cdrom instead of harddisk. So it is impossible to have a
> >>>>>>bootable CDROM in the VM without booting from it.
> >>>>>
> >>>>>-option-rom romfile=/root/roms/8xx_64.rom,bootindex=1
> >>>>
> >>>>Ok, works well, but I think than "-boot order=c" is buggy, right?
> >>>>
> >>>Wrong. "-boot order=c" tells seabios to boot from a HD, but for that
> >>>Seabios needs to actually know what is HD and what is not. Since Seabios
> >>>does not support scsi controller natively it only sees pci device and
> >>>has no idea that you have scsi disk there. It uses pci option rom to
> >>>boot from this unknown device.
> >>
> >>But as far as I remember therefore the option ROM registers through
> >>BIOS for INT 19h booting. So Seabios should know it that this is a
> >>harddisk.
> >It registers BEV. Otherwise you wouldn't be able to boot at all. In fact
> >it registers multiple BEVs (one for each attached scsi device). But BIOS
> >knows nothing about the device behind the BEV. It just jumps to BEV
> >address to boot from it when INT 19h is called. There may be scsi cdrom
> >there or even tape.
> 
> But to get rid of this problem typical BIOSes have an option whether
> they prefer to BOOT from SCSI (with an option ROM) or
> from the other devices. Then the option ROM typically boots from the
> first registered device.
> 
> I think this is a missing feature in Seabios.
> 
How is it missing if you just used it and confirmed that it worked?

--
			Gleb.