On Wed, 2011-11-23 at 15:39 +0100, Daniel Vetter wrote: > At least for the dmar+gfx+semaphores hang I can reproduce, just disabling > dmar with intel_iommu=igfx_off is not good enough and iirc the same holds > for the dmar+rc6 hangs reported. Um... let me restate that for clarity (and partly for Rajesh's benefit). The DMAR associated with the integrated graphics is *disabled*. Turned off. Not active. Ever. You have a problem when you enable the *other* DMAR units in the system, which should not be affecting the graphics device in any way. When you do this, you see 'hangs' with semaphores and RC6. Is there a better description of these 'hangs' somewhere? Is the hardware completely locked? These hangs go away when you disable the DMAR units. Again, that is the *other* DMAR units in the system that have nothing to do with graphics. While I'm getting quite used to DMAR-related errata, this one does make me stop and think 'wtf?'. It just seems so incongruous that disabling an *unrelated* IOMMU would make the problem go away, and it makes me wonder if it's actually a timing-related issue which is always there, but something about the use of DMAR for network/disk/etc. makes it more likely to trigger? We definitely need the hardware folks to get to the bottom of this one. -- dwmw2 -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 5818 bytes Desc: not available URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20111123/32652c1a/attachment.bin>
