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 15:12:44 +0100
Message-ID: <1439302364.9747.259.camel@citrix.com>
References: <55C413D5.7000709@huawei.com>
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To: Shannon Zhao <zhaoshenglong@huawei.com>, xen-devel <xen-devel@lists.xen.org>, Jan Beulich <jbeulich@suse.com>, Stefano
	Stabellini <stefano.stabellini@citrix.com>, Ian Campbell <ian.campbell@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>, David Vrabel <david.vrabel@citrix.com>
Cc: Hangaohuai <hangaohuai@huawei.com>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
List-Id: xen-devel@lists.xenproject.org

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.

Any _if_ there was a viable proposal along those lines then we could use it
and avoid the need for these HVM params perhaps?

Ian.