Re: [RFC PATCH qemu] spapr: Kill SLOF

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 13/01/2020 20:13, Andrea Bolognani wrote:
> On Wed, 2020-01-08 at 13:34 +1100, Alexey Kardashevskiy wrote:
>> On 07/01/2020 20:39, Andrea Bolognani wrote:
>>> On Tue, 2020-01-07 at 12:55 +1100, Alexey Kardashevskiy wrote:
>>>> Petitboot kernel+initramdisk almost replaces SLOF + GRUB.
>>>
>>> Is this necessarily a good thing?
>>
>> The bare metal host and the powernv machine in QEMU do not use grub,
>> they use petitboot which parses all grub configs and supports quite a lot.
> 
> How well does the distro integration work? Eg. if I change something
> in /etc/default/grub and then run grub2-mkconfig, can I expect my
> changes to be picked up?

Yes. Even the environment file (/boot/grub/grubenv).

> In which scenarios will that *not* work?

When/if grub adds a big new feature and petitboot won't have support for
it. Otherwise everything from GRUB is supported today.


>> Using Linux for a boot loader is not powerpc-only thing really, some
>> folks do this too (forgot who, just heard this at the KVM forum).
> 
> While other options are available and some architectures use
> something else entirely, GRUB is the de-facto standard across most
> of the non-obscure architectures.

True. I am thinking of extending this patch to support GRUB as well. Or
alternatively we could add a mode to GRUB to run in userspace under
petitboot's kernel.

It just seems quite an attractive idea to be able to boot from literally
anything without needing a ROM on whatever device is passed through to
the guest, or a driver in SLOF.


> I guess the question is whether it's more important to be consistent
> within the architecture or across them. I think the latter might be
> preferable, especially when we consider what I think is the most
> common scenario, that is, someone who's used to having GRUB on their
> x86 machine running a ppc64 guest on the cloud. The more skills they
> can automatically transfer over, the better.

True. petitboot is not horribly different though, and the user has to
take exact same steps as if it was GRUB.

>>> Personally I quite like the fact
>>> that I can use the same bootloader across x86, ppc64 and aarch64.
>>
>> I am not suggesting removing SLOF soon
> 
> Perhaps the patch subject shouldn't be "kill SLOF" then? ;)

This way I get more attention ;)


-- 
Alexey