On Tue, 27 Jan 2026 10:21:02 +0100,
Crystal Kolipe <kolipe.c@exoticsilicon.com> wrote:
> 
> On Tue, Jan 27, 2026 at 03:21:36AM +0100, Kirill A. Korinsky wrote:
> > The fallback forces VGA text mode even when the VGA probe fails, that
> > guaranteeing an early console, so boot can proceed even if GOP is absent
> > and no GPU driver is available.
> 
> With this patch, the kernel will be writing to memory locations and I/O ports
> that are traditionally associated with VGA hardware, despite no VGA hardware
> (or emulation thereof), necessarily being present.
> 
> Whilst it fixes your machine, how confident can we be that this is harmless on
> others?
> 
> It's perfectly valid to have no graphics hardware at all and run entirely from
> a serial console, so this could plausibly break machines that are currently
> working just fine.
> 

Well, here my assumption that on amd64, both the VGA legacy memory region
and I/O ports is still reserved and not used.

This machine has such region reserved, but you raised a good question: can
it be reused in the future for something else? My bet here that it will be
reserved for compatiblity, and this is quite small memory to be reused
anywere these days.

I only can think only about a check that goes by bios_memmap and checks that
this memory is actually reserved (it's true on this), but I have no idea how
to check that it isn't used for anything other that trivial BIOS_MAP_RES.

-- 
wbr, Kirill