On Thu, Oct 24, 2024 at 12:36:16PM +0200, Claudio Fontana wrote:
> What do we lose by just reverting things to the state that actually worked?
Well, the world is moving forward, devices getting more memory and
larger pci bars. GPUs can have multi-GB pci bars these days. nvidia
has a NPU with a 128 GB pci bar. Note this is larger than the whole
(initial) PAE address space. I want seabios supporting that kind of
devices well.
The range of configurations becomes more and more wide, with huge
devices as mentioned above on one end and old 32-bit guests on the
other end. Have seabios automatically setup itself turned out to be a
hard problem (as this thread clearly shows).
We already have a runtime config switch to force 32-bit friendly setup
(turn off long mode support in the vcpu).
We already have a heuristic to select the 32-bit friendly setup, which
right now is simply "no memory above 4G is present".
The options I see to move this forward:
(1) Tweak the heuristic.
(1a) Raise the memory limit.
(1b) Maybe also look at other things such as the machine type. The
'pc' machine type does not support pci express, so it is highly
unlikely that devices with huge pci bars will be used with it and
we could use that as another hint to better select the 32-bit
friendly setup.
(1c) Other ideas?
(2) Add a compile-time option (CONFIG_...) to force 32-bit friendly
setup unconditionally.
Comments?
take care,
Gerd
PS: sorry for the long delay, was offline in october and had quite a
email backlog afterwards ...
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