[Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters

[Jan Beulich]

>>> On 10.09.15 at 14:58, <ian.campbell at citrix.com> wrote:
> On Thu, 2015-09-10 at 13:15 +0100, Mark Rutland wrote:
> 
>> > In any case this should be separate from the shim ABI discussion.
>> 
>> I disagree; I think this is very much relevant to the ABI discussion.
>> That's not to say that I insist on a particular approach, but I think
>> that they need to be considered together.
> 
> Taking a step back, the reason for using the EFI stub parameters is only
> (AFAIK) in order to be able to locate the ACPI RDSP (the root table
> pointer), which as it happens is normally passed via one of the EFI
> firmware tables.
> 
> If there was a way to achieve that goal (i.e. another way to find the RSDP)
> without opening the can of UEFI worms then we could consider that opiton
> too.
> 
> a way != the legacy x86 thing of scanning low memory of the signature, of
> course.

But even x86 doesn't do that (other than as a fallback) on EFI. The
configuration table is available to Dom0 (via XENPF_firmware_info:
XEN_FW_EFI_INFO:XEN_FW_EFI_CONFIG_TABLE).

Jan