AMD Ryzen KVM/NPT/IOMMU issue

[Nick Sarnie]

On Wed, Jun 28, 2017 at 2:53 PM, Suravee Suthikulpanit
<Suravee.Suthikulpanit at amd.com> 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 :(
>
> S

Hi Suravee,

Did you get a chance to test this again with a more graphically
intense program such as the Unigine Heaven benchmark? This is still a
massive issue in the community.

Thanks,
Sarnex