Re: [PATCH] VT-d: add iommu=igfx_off option to workaround graphics issues

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Julien Grall <julien.grall@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>
Subject: Re: [PATCH] VT-d: add iommu=igfx_off option to workaround graphics issues
Date: Mon, 20 Jul 2015 09:27:13 +0100	[thread overview]
Message-ID: <55ACB0E1.6000505@citrix.com> (raw)
In-Reply-To: <55ABC817.5030601@citrix.com>

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).

~Andrew