Re: [PATCH v4 1/2] x86: return modified setup_data only if read as memory, not as file

[Paolo Bonzini]

On Wed, Sep 21, 2022 at 11:12 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> > Also I think it's cleaner if a reset callback puts the value back to
> > zero. fw_cfg already has fw_cfg_machine_reset, so perhaps the easiest
> > way is to add a FWCfgCallback reset_cb argument to just
> > fw_cfg_add_bytes_callback. If I am missing something and it's not
> > necessary I can do the cpu_to_le32 change myself or wait for you; in
> > any case I'll wait for either your ack or a v5.
>
> Actually, the idea is for the change to be permanent, since that
> represents how the system has actually been booted. Are there
> substantial changes possible to the firmware configuration on
> fw_cfg_machine_reset() that setting this back how it was would make a
> difference? Or do we benefit from having some consistency?

It's not a very practical thing to happen but I guess you could boot
UEFI twice, but the second time go to a CSM which could use the
setup_data. But really as you say it's just more consistent if reset
brings everything back to the pristine state, unless there's a good
reason to do so (which you agreed in the next message there isn't).

I'll queue v5, thanks!

Paolo