Re: AMD Ryzen KVM/NPT/IOMMU issue

[Suravee Suthikulpanit <Suravee.Suthikulpanit-5C7GfCeVMHo@public.gmane.org>]

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