Re: [PATCH RFC 1/3] xen/efi: Always query the console information and get GOP

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.02.2022 19:52, Julien Grall wrote:
> On 07/02/2022 08:46, Jan Beulich wrote:
>> On 06.02.2022 20:28, Julien Grall wrote:
>>> It is not entirely clear to me why the GOP was only fetched when
>>> the configuration file is used.
>>>
>>> I have tested this on RPI4 and it seems to work. Any chance this
>>> was done to workaround an x86 platform?
>>
>> This was done so in the context of making the code work for Arm. See
>> commit c38cf865ec82 ("EFI: ignore EFI commandline, skip console setup
>> when booted from GRUB"), the description of which explicitly says
>>
>> "Don't do EFI console or video configuration when booted by GRUB.  The EFI 
>> boot
>>   code does some console and video initialization to support native EFI boot 
>> from
>>   the EFI boot manager or EFI shell.  This initlization should not be done 
>> when
>>   booted using GRUB."
> 
> I read that and still couldn't figure out why this was done like that.
> 
>>
>> What you say now is effectively the opposite (and unlike back then
>> x86 is now able to use this code path as well, so needs considering
>> too). Cc-ing Daniel for possibly having a GrUB-side opinion.
> 
> I am quite interested to know the answer. Linux is able to use the EFI 
> framebuffer when booting via GRUB. So I am a bit puzzled why we are 
> preventing this setup on dom0/Xen.

To be honest - same here.

Jan