On Fri, Jun 16, 2017 at 06:29:23PM +0200, Joerg Roedel wrote: > Hi Bjorn, > > On Thu, Jun 15, 2017 at 02:15:45PM -0500, Bjorn Helgaas wrote: > > It was marked "superseded" in patchwork and thus off my radar. I > > don't remember if I did that or why. I changed it back to "New" so I > > won't forget about it. > > Great! > > > You mention (May 24) the original bug report. Can you include the URL > > for that? > > I think there were multiple reports, here is one I could still find: > > https://lists.linuxfoundation.org/pipermail/iommu/2017-March/020836.html > > > I admit I just don't have warm fuzzies that the problem is well > > understood. > > The current understanding (without my ability to debug the hardware > involved) is that the GPU in the Stoney systems gets into a weird state > when ATS invalidations are sent too fast and stops responding to the > iommu. > > The iommu then can't complete the invalidation commands and the driver > throws completion-wait loop timeout messages out. I'm still confused. Per Samuel (6dd9dbac-9b65-bc7c-bb08-413a05d09fc8@xxxxxxxx): Samuel> The other patch seems to fix this issue without disabling ATS. Samuel> Isn't that better? and Alex (BN6PR12MB1652DF4130FC792B71DD9974F7C00@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx): Alex> I talked to our validation team and ATS was validated on Stoney, Alex> so this patch is just working around something else. The other Alex> patch fixes it and is a valid optimization ... I'm confused about what this "other patch" is and whether we want that one, this one, or both. Bjorn
