From mboxrd@z Thu Jan  1 00:00:00 1970
From: ian.campbell@citrix.com (Ian Campbell)
Date: Thu, 10 Sep 2015 14:30:30 +0100
Subject: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of
 EFI stub parameters
In-Reply-To: <55F19D0202000078000A1B54@prv-mh.provo.novell.com>
References: <1441874516-11364-1-git-send-email-zhaoshenglong@huawei.com>
 <20150910095208.GA29293@leverpostej>
 <alpine.DEB.2.02.1509101116580.2672@kaball.uk.xensource.com>
 <20150910112418.GC29293@leverpostej>
 <alpine.DEB.2.02.1509101223580.2672@kaball.uk.xensource.com>
 <20150910121514.GE29293@leverpostej>
 <1441889905.24450.382.camel@citrix.com>
 <55F19D0202000078000A1B54@prv-mh.provo.novell.com>
Message-ID: <1441891830.24450.384.camel@citrix.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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.