From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@citrix.com>
Subject: Re: [PATCH] VT-d: add iommu=igfx_off option to
 workaround graphics issues
Date: Mon, 20 Jul 2015 11:19:10 +0100
Message-ID: <55ACCB1E.6000903@citrix.com>
References: <1437159952-4134-1-git-send-email-lantw44@gmail.com>
	<55ABC817.5030601@citrix.com> <55ACB0E1.6000505@citrix.com>
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: <55ACB0E1.6000505@citrix.com>
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: Andrew Cooper <andrew.cooper3@citrix.com>, Ting-Wei Lan <lantw44@gmail.com>, xen-devel@lists.xen.org
Cc: Yang Zhang <yang.z.zhang@intel.com>, Kevin Tian <kevin.tian@intel.com>, Jan Beulich <jbeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On 20/07/15 09:27, Andrew Cooper wrote:
> On 19/07/2015 16:53, Julien Grall wrote:
>> Hi,
>>
>> On 17/07/2015 20:05, Ting-Wei Lan wrote:
>>> When using Linux >= 3.19 (commit 47591df) as dom0 on some Intel Ironlake
>>> devices, It is possible to encounter graphics issues that make screen
>>> unreadable or crash the system. It was reported in freedesktop bugzilla:
>>>
>>> https://bugs.freedesktop.org/show_bug.cgi?id=90037
>>>
>>> As we still cannot find a proper fix for this problem, this patch adds
>>> iommu=igfx_off option that is similar to Linux intel_iommu=igfx_off for
>>> users to manually workaround the problem.
>>
>> I would prefer to see the introduction of intel_iommu parameter in the
>> vtd code rather than extending again the iommu parameter with intel
>> specific options in the common code which is both for ARM and x86.
> 
> Having the parsing for this option inside some x86 ifdefary, fine, but
> lets not have multiple iommu= options.  It is hard enough for people to
> drive one option (as people routinely get Xen and Linux command line
> options mixed up).

If you are concerned about mixing Xen and Linux command line options, it
would be more sensible to use intel_iommu=igfx_off on Xen to keep the
options exactly the same as Linux.

Regards,

-- 
Julien Grall