On Wed, Nov 23, 2011 at 02:01:54PM +0000, David Woodhouse wrote: > On Wed, 2011-11-23 at 11:26 +0100, Daniel Vetter wrote: > > On Tue, Nov 22, 2011 at 07:31:34PM -0800, Keith Packard wrote: > > > On Tue, 22 Nov 2011 20:15:31 +0000, Matthew Garrett <mjg at redhat.com> wrote: > > > > > > > So the user has to choose between 5W of power saving or having dmar? And > > > > we default to giving them dmar? I think that's going to come as a > > > > surprise to people. > > > > > > You'd have to go into the BIOS to turn this on for most machines at > > > least? > > > > > > But, yeah, it seems like we should be turning DMAR off unless explicitly > > > requested; I can't understand how you'd ever need this running native on > > > the hardware. Not exactly an area I care about deeply; I've always > > > worked hard to make sure all virtualization garbage is disabled on every > > > machine I use. > > > > Problem is that we need to disable dmar on the entire box, afaics. And I > > assume that a bunch of people abusing desktop boards as servers will call > > "regression" on that. > > Hm, do you really have to disable it for the entire box, or just the > graphics? 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. > Do we have a coherent erratum from Intel for the issues mentioned above > with DMAR+gfx+RC6? Afaik no errata applies to our dmar related troubles on snb. I've hoped that ppgtt would magically fix this, and it seems to help quite a bit for the semaphore hangs (but not everywhere). Couldn't yet look more into this. -Daniel -- Daniel Vetter Mail: daniel at ffwll.ch Mobile: +41 (0)79 365 57 48
