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

[Gerhard Wiesinger <lists@wiesinger.com>]

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.

Ciao,
Gerhard

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