From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: Design doc of adding ACPI support for arm64 on Xen
	- version 2
Date: Tue, 11 Aug 2015 15:59:00 +0100
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To: David Vrabel <david.vrabel@citrix.com>, Shannon Zhao <zhaoshenglong@huawei.com>, xen-devel <xen-devel@lists.xen.org>, Jan
	Beulich <jbeulich@suse.com>, Stefano Stabellini <stefano.stabellini@citrix.com>, Julien Grall <julien.grall@citrix.com>, Parth Dixit <parth.dixit@linaro.org>, Christoffer Dall <christoffer.dall@linaro.org>, Shannon Zhao <shannon.zhao@linaro.org>
Cc: Hangaohuai <hangaohuai@huawei.com>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
List-Id: xen-devel@lists.xenproject.org

On Tue, 2015-08-11 at 15:51 +0100, David Vrabel wrote:
> On 11/08/15 15:12, Ian Campbell wrote:
> > On Fri, 2015-08-07 at 10:11 +0800, Shannon Zhao wrote:
> > > 
> > [...]
> > > 3. Dom0 gets grant table and event channel irq information
> > > -----------------------------------------------------------
> > > As said above, we assign the hypervisor_id be "XenVMM" to tell Dom0 
> > > that
> > > it runs on Xen hypervisor.
> > > 
> > > For grant table, add two new HVM_PARAMs: 
> > > HVM_PARAM_GNTTAB_START_ADDRESS
> > > and HVM_PARAM_GNTTAB_SIZE.
> > 
> > The reason we expose this range is essentially to allow OS authors to 
> > take
> > a short cut by telling them about an IPA range which is unused, so it 
> > is
> > available for remapping the grant table into. On x86 there is a BAR on 
> > the
> > Xen platform PCI device which serves a similar purpose.
> > 
> > IIRC somebody (perhaps David V, CCd) had proposed at some point to make 
> > it
> > so that Linux was able to pick such an IPA itself by examining the 
> > memory
> > map or by some other scheme.
> 
> PVH in Linux uses ballooned pages which are vmap()'d into a virtually
> contiguous region.
> 
> See xlated_setup_gnttab_pages().

So somewhat more concrete than a proposal then ;-)

I don't see anything there which would be a problem on ARM, so we should
probably go that route there too (at least for ACPI, if not globally for
all ARM guests).

Ian.