Re: missing boot rom: is it really a fatal error?

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, May 07, 2023 at 08:56:23PM +0300, Michael Tokarev wrote:
> Hi!
> 
> In old good world ;), there was qemu which didn't require boot roms to be present
> for all devices for which bootrom file is defined, missing rom was just a warning.
> But this changed in 2014, 9 years ago, with this commit:
> 
> commit 178e785fb4507ec3462dc772bbe08303416ece47
> From: Marcel Apfelbaum <marcel.a@redhat.com>
> Date: Mon, 27 Oct 2014 19:34:41 +0200
> Subject: [PATCH] hw/pci: fixed error flow in pci_qdev_init
> 
>   Verify return code for pci_add_option_rom.
> 
> where inability to load rom file started being treated as an error.
> Up until now I didn't even know about this change, until today when someone bugged
> me about non-working qemu on debian, due to missing network boot roms (this a
> packaging issue due to me being unaware of the above change).
> 
> What is the reason to require boot roms to be present and throw an error if not?
> 
> I'm about to revert that old change on debian, to make it just a warning instead
> of an error (the code is different now, but the same principle applies), - because
> I dislike dependencies which are useless 99.9% of the time and are trivial to
> install when actually needed.
> 
> Thanks,
> 
> /mjt
> 

I advise against it.
If you boot guest on a system with boot rom not installed you will not
be able to migrate to a system with boot rom installed.
why not? because we don't know how big to make the rom BAR.
And users will not discover until much much later after they have
painted themselves into a corner.

-- 
MST