Re: [Qemu-devel] [PATCH 0/2] extboot reloaded.

[Alexander Graf <agraf@suse.de>]

Paul Brook wrote:
> On Tuesday 17 November 2009, Gerd Hoffmann wrote:
>   
>> On 11/17/09 13:36, Paul Brook wrote:
>>     
>>>>> In fact I'd much prefer to see extboot rewritten to just virtio-block.
>>>>>           
>>>> Hmm, I'd prefer something which is *not* used by the guest OS, so it is
>>>> a pure bootloader thing.  When using it to boot from scsi you don't want
>>>> to have the disk show up twice (as virtio and scsi) in the guest.
>>>>         
>>> You're assuming noone ever writes OS support for extboot...
>>>       
>> Which would be almost as silly as writing OS support for bios-int13 ...
>>     
>
> Not entirely. int13 is a software interface, extboot is a hardware interface.
> Look at it the other way round: If I already have my low performance boot 
> device exposed via extboot (on an otherwise diskless client), why should I 
> have to also expose it via virtio-blk just so that the guest can access it for 
> installing kernel upgrades.
>   

Because that's not what you'd use it for. That's what -kernel and
-initrd are there for.

IMHO having a BIOS backdoor is a good thing in general. If anyone wants
to destroy their user experience by writing a driver for that in their
OS, I'm good with that, but let's not expose things twice _to users_ as
the default case.


Alex