>-----Original Message----- >From: 'Joerg Roedel' [mailto:jroedel@xxxxxxx] >Sent: Wednesday, March 29, 2017 3:12 PM >To: Nath, Arindam >Cc: Deucher, Alexander; 'Joerg Roedel'; Bjorn Helgaas; linux- >pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Daniel Drake >Subject: Re: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS > >Hi Arindam, > >On Wed, Mar 29, 2017 at 07:15:42AM +0000, Nath, Arindam wrote: >> Joerg, as per my limited understanding of ATS, the ATC will respond to >> invalidation requests after making sure there are no in-flight DMA >> transactions with the address requested by IOMMU to be invalidated. >> Now since the IOMMU was sending invalidate command to GPU even >though >> there was no explicit page unmapping request from the graphics >> subsystem, we _might_ end up in a situation where the ATC takes longer >> than the invalidation timeout to respond to IOMMU. > >The maximum wait-time in the loop is 100ms. This should be more than >enough for the ATC to complete any in-flight transaction and flush its >internal TLB. > >If that is not enough, there is almost certainly something wrong with >the hardware. Actually what you said is correct. Before creating the patch, I had experimented with 1s and 10s invalidation timeout values, but none of them helped. Thanks, Arindam > > > > Joerg
