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SubjectRe: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters
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On Thu, 2015-09-10 at 07:08 -0600, Jan Beulich wrote:
> > > > On 10.09.15 at 14:58, <ian.campbell@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.

Indeed, I was referring legacy (non-EFI) mode.

> The
> configuration table is available to Dom0 (via XENPF_firmware_info:
> XEN_FW_EFI_INFO:XEN_FW_EFI_CONFIG_TABLE).

Under ARM we find out we are running under Xen from the ACPI tables, so
there is a chicken and egg situation there.

Not insoluble I'm sure, if we want to go down this route.
Ian.


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