Re: [Qemu-devel] [PATCH v2 2/2] hw/arm: Add Arm Enterprise machine type

[Peter Maydell]

On 30 August 2018 at 14:29, Ard Biesheuvel <address@hidden> wrote:
> How exactly the firmware figures out how many CPUs and how much memory
> we are running with is out of scope for this, and so I don't think
> there is a need to build something from scratch here: DT will do just
> fine, given that both EDK2 and ARM-TF have working DT code for these
> things.
>
> fw_cfg, on the other hand, is unsuitable for us. Generating ACPI
> tables in a different way from actual bare metal is not a good idea,
> given that things like RAS interact with ACPI as well, and fw_cfg is
> also exposed to the OS in the default mach-virt configuration. So we
> could tweak fw_cfg to be more suitable, but I think that does not
> improve the usefulness of our prototype at all.

fw_cfg is an entirely generic transport for passing named
data blobs from QEMU to the other end. You don't have to
pass ACPI table fragments over it the way we do for
virt and the x86 PC platforms if you don't want that.
It's true that it's visible to the OS in the sense that it's
a physical device in the system, but so is a hardware connection
to an SCP.

thanks
-- PMM