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Date:      Thu, 10 Sep 2015 14:30:30 +0100
From:      Ian Campbell <ian.campbell@citrix.com>
To:        Jan Beulich <JBeulich@suse.com>
Cc:        Mark Rutland <mark.rutland@arm.com>, "julien.grall@citrix.com" <julien.grall@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, "peter.huangpeng@huawei.com" <peter.huangpeng@huawei.com>, Shannon Zhao <zhaoshenglong@huawei.com>, "matt.fleming@intel.com" <matt.fleming@intel.com>, "ard.biesheuvel@linaro.org" <ard.biesheuvel@linaro.org>, "christoffer.dall@linaro.org" <christoffer.dall@linaro.org>, "leif.lindholm@linaro.org" <leif.lindholm@linaro.org>, "shannon.zhao@linaro.org" <shannon.zhao@linaro.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>, "daniel.kiper@oracle.com" <daniel.kiper@oracle.com>, "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>, "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>, "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject:   Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters
Message-ID:  <1441891830.24450.384.camel@citrix.com>
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>

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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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