Re: [PATCH v2] VT-d: add iommu=igfx option to workaround graphics issues

[Ting-Wei Lan <lantw44@gmail.com>]

Tian, Kevin 於 西元2015年07月31日 09:26 寫道:
>> From: Ting-Wei Lan [mailto:lantw44@gmail.com]
>> Sent: Sunday, July 26, 2015 12:58 AM
>>
>> 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 option to control whether Intel graphics IOMMU is enabled on
>> these devices. Running Xen with iommu=no-igfx is similar to running
>> Linux with intel_iommu=igfx_off, which disables IOMMU for Intel Ironlake
>> GPU. This can be used by users to manually workaround the problem before
>> a fix is available for i915 driver.
>>
>> Signed-off-by: Ting-Wei Lan <lantw44@gmail.com>
>> ---
>> Changed since v1:
>>    * Replace igfx_off with igfx
>>
>> This patch is currently only build-tested because I don't have access to
>> the hardware that have graphics issues this week. I will test this new
>> patch next week.
>>
>>   docs/misc/xen-command-line.markdown  | 12 +++++++++++-
>>   xen/drivers/passthrough/iommu.c      |  3 +++
>>   xen/drivers/passthrough/vtd/quirks.c |  2 +-
>>   xen/include/xen/iommu.h              |  2 +-
>>   4 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/docs/misc/xen-command-line.markdown
>> b/docs/misc/xen-command-line.markdown
>> index 13f03ad..6262be6 100644
>> --- a/docs/misc/xen-command-line.markdown
>> +++ b/docs/misc/xen-command-line.markdown
>> @@ -793,7 +793,7 @@ debug hypervisor only).
>>   > Default: `new` unless directed-EOI is supported
>>
>>   ### iommu
>> -> `= List of [ <boolean> | force | required | intremap | qinval | snoop | sharept |
>> dom0-passthrough | dom0-strict | amd-iommu-perdev-intremap | workaround_bios_bug
>> | verbose | debug ]`
>> +> `= List of [ <boolean> | force | required | intremap | qinval | snoop | sharept |
>> dom0-passthrough | dom0-strict | amd-iommu-perdev-intremap | workaround_bios_bug
>> | igfx | verbose | debug ]`
>>
>>   > Sub-options:
>>
>> @@ -867,6 +867,16 @@ debug hypervisor only).
>>   >> ignored (normally IOMMU setup fails if any of the devices listed by a DRHD
>>   >> entry aren't PCI discoverable).
>>
>> +> `igfx` (VT-d)
>> +
>> +> Default: `true`
>> +
>> +>> Enable IOMMU for Intel Calpella/Ironlake devices. This option does not
>> +>> affect grahpics IOMMU on other devices. The intended usage of this option
>> +>> is `no-igfx`, which is silimar to Linux `intel_iommu=igfx_off` option used
>> +>> to workaround graphics issues. If adding `no-igfx` fixes anything, you
>> +>> should file a bug reporting the problem.
>> +
>
> For above description let's make it general, i.e Enable IOMMU for Intel Processor
> Graphics devices. You can list Calpella/Ironlake as the example, but not the only
> target. :-)

no-igfx only works with Calpella/Ironlake because 
is_igd_vt_enabled_quirk() contains this code:

if ( !IS_ILK(ioh_id) )
     return 1;

The newly added variable iommu_igfx only changes the return value of 
is_igd_vt_enabled_quirk() when IS_ILK(ioh_id) is true. I don't know 
whether we will need no-igfx on other Intel graphics devices because I 
don't many devices to test and I don't have other devices that have this 
problem.

>
> Thanks
> Kevin
>


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel