Hi,
On 22/10/2020 02:43, Elliott Mitchell wrote:
Linux requires UEFI support to be enabled on ARM64 devices. While many
ARM64 devices lack ACPI, the writing seems to be on the wall of UEFI/ACPI
potentially taking over. Some common devices may need ACPI table
support.
Presently I think it is worth removing the dependancy on CONFIG_EXPERT.
The idea behind EXPERT is to gate any feature that is not considered to
be stable/complete enough to be used in production.
I don't consider the ACPI complete because the parsing of the IORT (used
to discover SMMU and GICv3 ITS) is not there yet.
I vaguely remember some issues on system using SMMU (e.g. Thunder-X)
because Dom0 will try to use the IOMMU and this would break PV drivers.
Therefore I think we at least want to consider to hide SMMUs from dom0
before removing EXPERT. Ideally, I would also like the feature to be
tested in Osstest.
The good news is Xen Project already has systems (e.g. Thunder-X,
Softiron) that can supported ACPI. So it should hopefully be a matter to
tell them to boot with ACPI rather than DT.
Cheers,
--
Julien Grall
