Re: [Qemu-devel] [Linaro-acpi] [RFC PATCH 0/7] hw/arm/virt: Dynamic ACPI v5.1 table generation

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/11/2014 11:38, Mark Rutland wrote:
> > I share your concern, but running another UEFI instance for Dom0 doesn't
> > seem like a viable alternative either.  Why is this a problem on ARM and
> > not on x86 though?
> 
> I believe that on x86 the fallback for !UEFI would be the e820 memory
> map, which provides info regarding the type of the memory mapping, as
> opposed to just the base + size. That said, I'm not that familiar with
> e820, and from a quick look the provided information doesn't seem to be
> that detailed.

The e820 memory map is only part of it.  On x86 !UEFI you are supposed
to scan low memory for magic signatures that provides pointers to the
SMBIOS and ACPI tables.

As Christoffer said, "the good old PC". :)

SeaBIOS fishes out information from fw_cfg, and puts it in low memory.
On ARM you could use DT binary blobs instead of fw_cfg, as proposed
already (I don't remember if it was in this thread or IRC).  Then if you
want to go !UEFI you can extract the tables from those binary blobs.

Paolo