From mboxrd@z Thu Jan 1 00:00:00 1970 From: geoff--- via iommu Subject: Re: AMD Ryzen KVM/NPT/IOMMU issue Date: Tue, 24 Oct 2017 16:15:24 +1100 Message-ID: References: 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: In-Reply-To: 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 Further to this I have verified that IOMMU is working fine, traces and additional printk's added to the kernel module were used to check. All accesses are successful and hit the correct addresses. However profiling under Windows shows there might be an issue with IRQs not reaching the guest. When FluidMark is running at 5fps I still see excellent system responsiveness with the CPU 90% idle and the GPU load at 6%. When switching PhysX to CPU mode the GPU enters low power mode, indicating that the card is no longer in use. This would seem to confirm that the GPU is indeed in use by the PhysX API correctly. My assumption now is that the IRQs from the video card are getting lost. I could be completely off base here but at this point it seems like the best way to proceed unless someone cares to comment. -Geoff On 2017-10-24 10:49, geoff-9M2dFRIgpjGrDvn5mFPilA@public.gmane.org wrote: > 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/