Bug 177791

Summary:	screen flickering with intel_iommu=on
Product:	Virtualization	Reporter:	v
Component:	kvm	Assignee:	virtualization_kvm
Status:	RESOLVED INSUFFICIENT_DATA
Severity:	low	CC:	A.Fiergolski+kernelBugzilla, kolAflash, szg00000
Priority:	P1
Hardware:	Intel
OS:	Linux
Kernel Version:	4.8,4.9	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	kernel config

Description v 2016-10-17 04:14:08 UTC

Hello,

I have found a strange bug with IOMMU: when I enable the IOMMU and put the mouse cursor at any width on 885'th or 1019'th pixel from the top, the screen glitches appear, like flickering or tearing. 
It's difficult to explain, please see the videos: 
IOMMU enabled: http://robolab.it/iommu/iommu_on.mp4 (28M)
IOMMU disabled: http://robolab.it/iommu/iommu_off.mp4 (3.7M)

The bug appears with Linux 4.7.6, 4.7.7, 4.8.0 and 4.8.1. 
I have not tried the current releases (4.8.2 and 4.7.8) yet.

System: Clevo P640RE laptop with Intel Core i7-6700HQ CPU
OS: openSuSE 13.2 x86_64

Comment 1 v 2016-10-17 04:39:41 UTC

Created attachment 241861 [details]
kernel config

Forgot to mention that nothing new appears in dmesg when the screen flickers.

Comment 2 v 2016-10-18 11:39:03 UTC

Update: booting with "intel_iommu=on,igfx_off" removes screen flickering with mouse cursor on 885th and 1019th pixels height.

Comment 3 kolAflash 2016-10-21 15:54:28 UTC

Maybe related: https://bugs.freedesktop.org/show_bug.cgi?id=97450

Comment 4 v 2016-11-17 09:29:25 UTC

I have installed the kernel 4.8.7 because I saw many improvements with i915 in the changelog, but the problem still persists.

Comment 5 v 2017-02-20 08:26:33 UTC

The problem still persists in kernel version 4.9.11. 

However I've changed the Importance field to "Low" and Status to RESOLVED because I can live with the workaround "intel_iommu=on,igfx_off" and seems that this bug does not affect other people.

Comment 6 Adrian 2017-11-06 10:23:29 UTC

Hello,
Could you point a parch which fixes this issue ?
Current Ubuntu kernel seems to suffer this bug.

Comment 7 Adrian 2017-11-06 10:24:41 UTC

I am sorry for last comment. I chose wrong tab in the browser.