On Tue, Mar 28, 2017 at 09:13:23PM +0000, Deucher, Alexander wrote: > If I understand Arindam's patch correctly, it only flushes TLB entries > for domains in the flush queue whereas the previous behavior was to > flush all domains. If there was no TLB flush in the queue for that > domain, could flushing it cause a problem? No, that can't cause a problem. An io/tlb flush for the device is just a message that the device should invalidate its own tlb. The device can't know and doesn't need to know whether the page-tables it used to fill the tlb really changed. As it looks, the problem we are seeing here is that we are sending a large amount of these requests to the GPU device, and wait for its completion every time. This shouldn't be a problem for ATS devices, but the GPU here seems to fail at some point and doesn't answer to the invalidation request anymore, causing the completion-wait loop timeouts. Arindam's patch makes the high flush-frequency less likely, but it can still happen, depending on how the GPU is used. So its the best to keep ATS disabled on the device as it doesn't work correctly and we risk running in the same problem again when we leave it enabled and just make the trigger less likely. Joerg
