Re: [Qemu-devel] Re: [PATCH 0/2] port over extboot from kvm

[Avi Kivity]

On 09/08/2009 05:32 PM, Anthony Liguori wrote:
> Gerd Hoffmann wrote:
> > On 09/08/09 15:47, Jan Kiszka wrote:
> >
> > > Before setting this definitely useful feature in stone, I have two
> > > questions though:
> > >
> > >   - -drive ...,boot=on is logically in conflict with -boot. Yes, -boot
>
> x86 boot is strange.  The BIOS boots from the "first hard disk"  What 
> extboot allows you do to is redefine to the bios what constitutes the 
> "first hard disk".

It's not just booting - it's the int 0x13 interface.  Grub for example 
continues to use it and can boot from the second hard disk if desired.


> This is the motivation for making it a -drive option.  Perhaps this is 
> something we want to hide from the user but that was the motivation.

I agree with this and I think we should extend it to boot=0x80|0x81....  
boot=on is an alias to boot=0x80.

> For instance, it would not be possible to define a boot sequence of 
> "first virtio disk, then second virtio disk, then cdrom" because we 
> can't present two disks as the first hard disk.
>
> If extboot supported BCV and our bios did, the above would be possible.


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