Re: VW ELF loader

[Paolo Bonzini]

On 05/02/20 06:58, David Gibson wrote:
>> Yes, SLOF is big and slow.  petitboot is not petit at all either, and
>> has the disadvantage that you have to find a way to run GRUB afterwards.
> Well, not usually.  Petitboot parses grub configuration itself, which
> means that generally from the OS / installer point of view it looks
> like grub, even though it's not from the actual bootstrapping point of
> view.

Ok, sorry about that.  I need to learn a bit more.

>>  But would a similarly minimal OF implementation (no network, almost no
>> interpret so no Forth, device tree built entirely in the host, etc.) be
>> just as big and slow?
> 
> So, as actual OF implementations go, SLOF is already pretty minimal
> (hence "Slim Line Open Firmware").  If there's no Forth, it's really
> not OF any more, just something mimicing some of OF's interfaces.

Right, not unlike what you get with vof=on. :)  I'm not against at all
that idea.  I just don't understand what you refer to below as (2).
Does petitboot not have the problem because it kexecs the new kernel?

Paolo

> But the difficulty of SLOF isn't really its bigness or slowness in any
> case (the slowness is just an additional irritation).  The two big
> issues are 1) that it's written in an obscure language and 2)
> synchronizing its state with things that require host side
> involvement.
> 
> Rewriting a minimal guest side not-OF would partly address (1) (but
> there's still the logistical pain of having to build and insert it),
> and wouldn't address (2) at all.