From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH 7/7] xen/arm: Blacklist some sun7i UARTs
Date: Fri, 27 Sep 2013 18:04:57 +0100
Message-ID: <5245BAB9.5000208@citrix.com>
References: <1379693872.8994.37.camel@hastur.hellion.org.uk>
	<1379693918-24067-7-git-send-email-ian.campbell@citrix.com>
	<523C9BC3.10702@linaro.org>
	<1379713262.8994.56.camel@hastur.hellion.org.uk>
	<523E0161.6020805@linaro.org>
	<1379860820.30708.18.camel@dagon.hellion.org.uk>
	<5245BA11.1080903@linaro.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <5245BA11.1080903@linaro.org>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Julien Grall <julien.grall@linaro.org>
Cc: xen-devel@lists.xen.org, tim@xen.org, Ian Campbell <Ian.Campbell@citrix.com>, stefano.stabellini@eu.citrix.com
List-Id: xen-devel@lists.xenproject.org

On 27/09/13 18:02, Julien Grall wrote:
> On 09/22/2013 03:40 PM, Ian Campbell wrote:
>> On Sat, 2013-09-21 at 21:28 +0100, Julien Grall wrote:
>>> On 09/20/2013 10:41 PM, Ian Campbell wrote:
>>>> On Fri, 2013-09-20 at 20:02 +0100, Julien Grall wrote:
>>>>
>>>>>> +    /*
>>>>>> +     * These UARTs share a page with the Xen console UART, so we don't
>>>>>> +     * want to map them through.
>>>>>> +     */
>>>>>> +    DT_MATCH_PATH("/soc@01c00000/serial@01c28000"),
>>>>>> +    DT_MATCH_PATH("/soc@01c00000/serial@01c28400"),
>>>>>> +    DT_MATCH_PATH("/soc@01c00000/serial@01c28800"),
>>>>>> +    DT_MATCH_PATH("/soc@01c00000/serial@01c28c00"),
>>>>> Can we blacklist all the UARTs via a DT_MATCH_COMPATIBLE? It's better
>>>>> than relying on the path that can be changed easily in the device tree.
>>>> There are other UARTS (at 0x1c29xxx) which could safely be exposed to
>>>> dom0. Perhaps it is better to just blacklist the whole lot though.
>>> These UARTs also share the same page, what prevents the user to use 
>>> these UARTs?
>> Nothing, but because they don't share a page with the xen UART they
>> don't cause it to get exposed to dom0.
> My question wasn't clear. What does prevent the user to use another UART
> for Xen?
>

Nothing "prevents" it.  That is the problem.  If several UARTs are on
the same page, Xen cannot safely isolate its UART from dom0/domU.

~Andrew