Re: [PATCH v1 1/2] arm: Add ability to relocate Xen in over 4GB space

From: Ian Campbell <ian.campbell@citrix.com>
To: Andrii Anisov <andrii.anisov@globallogic.com>
Cc: Iurii Konovalenko <iurii.konovalenko@globallogic.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	Julien Grall <julien.grall@linaro.org>, Tim Deegan <tim@xen.org>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Julien Grall <julien.grall@citrix.com>
Subject: Re: [PATCH v1 1/2] arm: Add ability to relocate Xen in over 4GB space
Date: Fri, 8 May 2015 17:02:55 +0100	[thread overview]
Message-ID: <1431100975.2660.529.camel@citrix.com> (raw)
In-Reply-To: <CAGQvs6hgUd_M5GJ-6qm0VzBQP-tV=Z4wSu5sphOkGzWcGpTX3w@mail.gmail.com>

On Wed, 2015-04-08 at 20:24 +0300, Andrii Anisov wrote:

I was thinking about this a little more...

> The context here is pretty simple: just a workaround of the real
> system limitations:
>      1. Renesas R-Car H2 evaluation board lager has 4GB of RAM, 2GB
>         mapped under 4GB boundary and 2GB over. 
>      2. The R-Car2 chip has IOMMU's for almost all active devices
>         except GPU. 
>      3. Within our system we need one user domain with 2GB of RAM and
>         dedicated GPU.
>      4. While doing PoC we have no access to the GPU driver(and
>         firmware) sources to introduce swiotlb here. 
> Having no option to handle GPU driver addressing with iommu (2) or
> swiotlb(4), it was decided to place the user domain described in 3
> within RAM below 4GB with 1:1 mapping. Therefore we needed to move all
> the rest (XEN, rest of domains) under 4GB.

Xen itself (i.e. .text and .data, no the heap etc) is at most 2MB. Are
your constraints such that at a 2GB-2MB (i.e. 2046M) domain would not be
acceptable?

Ian.