On Wed, Nov 16, 2011 at 18:16, Keith Packard <keithp at keithp.com> wrote: > On Wed, 16 Nov 2011 16:49:40 +0100, Daniel Vetter <daniel.vetter at ffwll.ch> wrote: > >> So we need to check whether DMAR is enabled (on the >> entire system, i.e. the variable exported for the ilk workaround is >> not good enough) > > Can you figure out what *would* be sufficient? Getting semaphores turned > on for the 99% who aren't enabling VT-d would be a fairly nice > performance improvement. Last time I've played around with all the combinations, only intel_iommu=off was good enough to prevent the hang. intel_iommu=igd_off still hangs (which is what the current value exported by the dmar code dopends on, iirc). If I remember things correctly, intel_iommu=off also reliably works around issues for all reporters (both semaphores and rc6). And for reproducing it, at least here the key ingredient seems to be a kde4 desktop. Spare the jokes ;-) -Daniel -- Daniel Vetter daniel.vetter at ffwll.ch - +41 (0) 79 365 57 48 - http://blog.ffwll.ch
