From mboxrd@z Thu Jan 1 00:00:00 1970 From: geoff--- via iommu Subject: AMD Ryzen KVM/NPT/IOMMU issue Date: Tue, 24 Oct 2017 10:49:36 +1100 Message-ID: Reply-To: geoff-9M2dFRIgpjGrDvn5mFPilA@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi, I realize this is an older thread but I have spent much of today trying to diagnose the problem. I have discovered how to reliably reproduce the problem with very little effort. It seems that reproducing the issue has been hit and miss for people as it seems to primarily affect games/programs that make use of nVidia PhysX. My understanding of npt's inner workings is quite primitive but I have still spent much of my time trying to diagnose the fault and identify the cause. Using the free program FluidMark[1] it is possible to reproduce the issue, where on a GTX 1080Ti the rendering rate drops to around 4 fps with npt turned on, but if turned off the render rate is in excess of 60fps. I have produced traces for with and without ntp enabled during these tests which I can provide if it will help. So far I have been digging through how npt works and trying to glean as much information as I can from the source and the AMD specifications but much of this and how mmu works is very new to me so progress is slow. If anyone else has looked into this and has more information to share I would be very interested. Kind Regards, Geoffrey McRae HostFission https://hostfission.com [1]: http://www.geeks3d.com/20130308/fluidmark-1-5-1-physx-benchmark-fluid-sph-simulation-opengl-download/