On Thu, 29 Jun 2017 01:53:57 +0700 Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx> wrote: > On 6/29/17 00:26, Steven Walter wrote: > >> So, I'm trying to reproduce this issue on the Ryzen system w/ the following > >> setup: > >> > >> * Host kernel v4.11 (with this patch https://lkml.org/lkml/2017/6/23/295) > >> > >> * guest VM RHEL7.3 > >> > >> * guest graphic driver = radeon > >> > >> * qemu-system-x86_64 --version > >> QEMU emulator version 2.9.50 (v2.9.0-1659-g577caa2-dirty) > >> > >> * kvm-amd npt=1 > >> > >> * dGPU is 08:00.0 VGA compatible controller: Advanced Micro Devices, Inc. > >> [AMD/ATI] Tobago PRO [Radeon R7 360 / R9 360 OEM] (rev 81) > >> > >> * qemu-system-x86_64 -smp 4 -enable-kvm -M q35 -m 4096 -cpu host -bios > >> /usr/share/qemu/bios.bin -device > >> ioh3420,bus=pcie.0,addr=1c.0,multifunction=on,port=1,chassis=1,id=root.1 > >> -drive file=/sandbox/vm-images/rhel7.3.qcow2,if=virtio,id=disk0 -net none > >> -vga none -nodefaults -device > >> vfio-pci,host=08:00.0,x-vga=on,addr=0.0,multifunction=on,bus=root.1,romfile=/sandbox/vm-images/vbios.rom > >> -usb -device usb-host,hostbus=3,hostport=1 -device > >> usb-host,hostbus=3,hostport=3 -device vfio-pci,host=0000:08:00.1 -device > >> vfio-pci,host=0000:09:00.0 > >> > >> With this setup, I am able to pass-through the dGPU and run the following > >> test: > >> * Starting up the guest w/ full GNOME GUI on the attached monitor. > >> * glxgears (running @ 60 FPS) > >> * Playing 1080p HD video on Youtube > >> > >> I am not noticing issues here. What kind of test are you running in the > >> guest VM? > > Try running the open source game "torcs" inside the VM. I think > > you'll find that there's a very noticeable performance different > > between npt=1 and npt=0 > > Hm.. actually torcs seems to be running fine w/ npt=1 setup. Although I think my > driving skill is ~20% worse :( A clarification on the issue, it's not that these games/benchmarks don't work or aren't playable, it's that they run slower (as measured by framerate) with npt=1 vs npt=0. A virtualized guest on AMD hardware is hindered either by lower graphics performance (npt=1) or higher CPU virtualization overhead (npt=0) for high intensity games or graphics workloads. Intel's equivalent ept feature does not have this issue. I would encourage looking at the framerate for one mode vs the other before drawing any conclusions on whether it's working well. Thanks, Alex
