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

[Julien Grall <julien.grall@xxxxxxxxxx>]

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

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