Ryzen CPU (3700X) doesn't support hyperthreading? (libvirt error) [Solved]

Operating Systems & Open Source Virtualization
1

Hi all, quick question, because I usually don’t want to bother folks - but I’m having a Google fail on this one.

I can’t seem to get my Ryzen CPU passed through with SMT support. The Win10 client simply reports 14 logical cores with no SMT - running the WMIC command shows the same amount of logical cores, as there is processors - instead of 7 cores with 14 logical processors.

(I’m doing single GPU passthrough so basically was going to give the VM everything except a single core to handle I/O, emulation tasks and host housekeeping).

/var/log/libvirt/qemu/Win10.log shows:
“This family of AMD CPU doesn’t support hyperthreading”

I was trying to improve performance and found I was better off pinning only the full cores and leaving the SMT cores out of the VM. My guess is that this is because the Windows scheduler has no clue which cores are what. This is a bit annoying - as it leaves CPU horsepower unusable.

So, am I missing something or is there really no way to passthrough Ryzen SMT cores in a way that Windows can recognise?

XML below if it helps :slight_smile:
(note that this is the current config - with no SMT cores passed through , just 7 cores with 1 thread each, I can post the other config if desired.)

<domain type="kvm">
  <name>Win10</name>
  <uuid>b7b239fb-8a10-40fc-a2a7-aba7c8fbe562</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://microsoft.com/win/10"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit="KiB">16777216</memory>
  <currentMemory unit="KiB">16777216</currentMemory>
  <memoryBacking>
    <hugepages/>
  </memoryBacking>
  <vcpu placement="static">7</vcpu>
  <iothreads>1</iothreads>
  <cputune>
    <vcpupin vcpu="0" cpuset="1"/>
    <vcpupin vcpu="1" cpuset="2"/>
    <vcpupin vcpu="2" cpuset="3"/>
    <vcpupin vcpu="3" cpuset="4"/>
    <vcpupin vcpu="4" cpuset="5"/>
    <vcpupin vcpu="5" cpuset="6"/>
    <vcpupin vcpu="6" cpuset="7"/>
    <emulatorpin cpuset="0,8"/>
    <iothreadpin iothread="1" cpuset="0,8"/>
  </cputune>
  <os firmware="efi">
    <type arch="x86_64" machine="pc-q35-6.2">hvm</type>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv mode="custom">
      <relaxed state="on"/>
      <vapic state="on"/>
      <spinlocks state="on" retries="8191"/>
    </hyperv>
    <vmport state="off"/>
  </features>
  <cpu mode="host-passthrough" check="none" migratable="on">
    <topology sockets="1" dies="1" cores="7" threads="1"/>
    <feature policy="disable" name="svm"/>
  </cpu>
  <clock offset="localtime">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
    <timer name="hypervclock" present="yes"/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled="no"/>
    <suspend-to-disk enabled="no"/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type="block" device="disk">
      <driver name="qemu" type="raw"/>
      <source dev="/dev/sdc"/>
      <target dev="vda" bus="virtio"/>
      <address type="pci" domain="0x0000" bus="0x02" slot="0x00" function="0x0"/>
    </disk>
    <controller type="usb" index="0" model="qemu-xhci" ports="15">
      <address type="pci" domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
    </controller>
    <controller type="pci" index="0" model="pcie-root"/>
    <controller type="pci" index="1" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="1" port="0x10"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x0" multifunction="on"/>
    </controller>
    <controller type="pci" index="2" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="2" port="0x11"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x1"/>
    </controller>
    <controller type="pci" index="3" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="3" port="0x12"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x2"/>
    </controller>
    <controller type="pci" index="4" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="4" port="0x13"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x3"/>
    </controller>
    <controller type="pci" index="5" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="5" port="0x14"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x4"/>
    </controller>
    <controller type="pci" index="6" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="6" port="0x15"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x5"/>
    </controller>
    <controller type="pci" index="7" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="7" port="0x16"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x6"/>
    </controller>
    <controller type="pci" index="8" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="8" port="0x17"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x7"/>
    </controller>
    <controller type="pci" index="9" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="9" port="0x18"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x0" multifunction="on"/>
    </controller>
    <controller type="pci" index="10" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="10" port="0x19"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x1"/>
    </controller>
    <controller type="pci" index="11" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="11" port="0x1a"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x2"/>
    </controller>
    <controller type="pci" index="12" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="12" port="0x1b"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x3"/>
    </controller>
    <controller type="pci" index="13" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="13" port="0x1c"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x4"/>
    </controller>
    <controller type="pci" index="14" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="14" port="0x1d"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x5"/>
    </controller>
    <controller type="sata" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x1f" function="0x2"/>
    </controller>
    <interface type="network">
      <mac address="52:54:00:c3:d1:06"/>
      <source network="default"/>
      <model type="virtio"/>
      <address type="pci" domain="0x0000" bus="0x05" slot="0x00" function="0x0"/>
    </interface>
    <input type="mouse" bus="ps2"/>
    <input type="keyboard" bus="ps2"/>
    <audio id="1" type="none"/>
    <hostdev mode="subsystem" type="pci" managed="yes">
      <source>
        <address domain="0x0000" bus="0x09" slot="0x00" function="0x0"/>
      </source>
      <address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
    </hostdev>
    <hostdev mode="subsystem" type="pci" managed="yes">
      <source>
        <address domain="0x0000" bus="0x09" slot="0x00" function="0x1"/>
      </source>
      <address type="pci" domain="0x0000" bus="0x07" slot="0x00" function="0x0"/>
    </hostdev>
    <hostdev mode="subsystem" type="usb" managed="yes">
      <source>
        <vendor id="0x046d"/>
        <product id="0xc08b"/>
      </source>
      <address type="usb" bus="0" port="3"/>
    </hostdev>
    <hostdev mode="subsystem" type="usb" managed="yes">
      <source>
        <vendor id="0x1532"/>
        <product id="0x025e"/>
      </source>
      <address type="usb" bus="0" port="4"/>
    </hostdev>
    <hostdev mode="subsystem" type="usb" managed="yes">
      <source>
        <vendor id="0x10f5"/>
        <product id="0x2154"/>
      </source>
      <address type="usb" bus="0" port="5"/>
    </hostdev>
    <memballoon model="virtio">
      <address type="pci" domain="0x0000" bus="0x04" slot="0x00" function="0x0"/>
    </memballoon>
  </devices>
</domain>
2

You should be able to enable SMT by adding the topoext feature in your XML as per the Arch Wiki

 <cpu mode='host-passthrough' check='none'>
   <topology sockets='1' cores='4' threads='2'/>
   <feature policy='require' name='topoext'/>
 </cpu>
3

exactly.
And this is indeed an important optimization, as it allows the scheduler to make better decisions on where to place a process.

@Shifty_Mick might want to consider using virt-manager, which makes these settings available via a nice GUI(you can easily use virt-manager on remote servers by adding a qemu+ssh:// connection).

4

@CaptClock you sir, are the man! I had enabled that setting before but was experiencing some instability (turned out to be unrelated) but forgot to put it back in the XML.

Working as expected now, so many thanks! Framerates are up and Windows is now correctly reporting the correct number and type of cores! I’ll revisit the Arch wiki and see if I’ve missed anything else, as I’m still about 1000points down on the Valley benchmark - with my 1070 passed through, as opposed to running the benchmark on bare metal (~6000 vs ~7000).

@max1220 thanks for the tip, but I’m already using the virtual machine manager, should it have added that topoext feature policy for me? As it didn’t seem to.

(Although it’s not impossible that I may have accidentally removed it at some point.)

For the sake of completeness I’ll post the updated XML below:

<domain type="kvm">
  <name>Win10</name>
  <uuid>b7b239fb-8a10-40fc-a2a7-aba7c8fbe562</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://microsoft.com/win/10"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit="KiB">16777216</memory>
  <currentMemory unit="KiB">16777216</currentMemory>
  <memoryBacking>
    <hugepages/>
  </memoryBacking>
  <vcpu placement="static">14</vcpu>
  <iothreads>1</iothreads>
  <cputune>
    <vcpupin vcpu="0" cpuset="1"/>
    <vcpupin vcpu="1" cpuset="9"/>
    <vcpupin vcpu="2" cpuset="2"/>
    <vcpupin vcpu="3" cpuset="10"/>
    <vcpupin vcpu="4" cpuset="3"/>
    <vcpupin vcpu="5" cpuset="11"/>
    <vcpupin vcpu="6" cpuset="4"/>
    <vcpupin vcpu="7" cpuset="12"/>
    <vcpupin vcpu="8" cpuset="5"/>
    <vcpupin vcpu="9" cpuset="13"/>
    <vcpupin vcpu="10" cpuset="6"/>
    <vcpupin vcpu="11" cpuset="14"/>
    <vcpupin vcpu="12" cpuset="7"/>
    <vcpupin vcpu="13" cpuset="15"/>
    <emulatorpin cpuset="0,8"/>
    <iothreadpin iothread="1" cpuset="0,8"/>
  </cputune>
  <os firmware="efi">
    <type arch="x86_64" machine="pc-q35-6.2">hvm</type>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv mode="custom">
      <relaxed state="on"/>
      <vapic state="on"/>
      <spinlocks state="on" retries="8191"/>
    </hyperv>
    <vmport state="off"/>
  </features>
  <cpu mode="host-passthrough" check="none" migratable="on">
    <topology sockets="1" dies="1" cores="7" threads="2"/>
    <feature policy="require" name="topoext"/>
    <feature policy="disable" name="svm"/>
  </cpu>
  <clock offset="localtime">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
    <timer name="hypervclock" present="yes"/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled="no"/>
    <suspend-to-disk enabled="no"/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type="block" device="disk">
      <driver name="qemu" type="raw"/>
      <source dev="/dev/sdc"/>
      <target dev="vda" bus="virtio"/>
      <address type="pci" domain="0x0000" bus="0x02" slot="0x00" function="0x0"/>
    </disk>
    <controller type="usb" index="0" model="qemu-xhci" ports="15">
      <address type="pci" domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
    </controller>
    <controller type="pci" index="0" model="pcie-root"/>
    <controller type="pci" index="1" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="1" port="0x10"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x0" multifunction="on"/>
    </controller>
    <controller type="pci" index="2" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="2" port="0x11"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x1"/>
    </controller>
    <controller type="pci" index="3" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="3" port="0x12"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x2"/>
    </controller>
    <controller type="pci" index="4" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="4" port="0x13"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x3"/>
    </controller>
    <controller type="pci" index="5" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="5" port="0x14"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x4"/>
    </controller>
    <controller type="pci" index="6" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="6" port="0x15"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x5"/>
    </controller>
    <controller type="pci" index="7" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="7" port="0x16"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x6"/>
    </controller>
    <controller type="pci" index="8" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="8" port="0x17"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x7"/>
    </controller>
    <controller type="pci" index="9" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="9" port="0x18"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x0" multifunction="on"/>
    </controller>
    <controller type="pci" index="10" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="10" port="0x19"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x1"/>
    </controller>
    <controller type="pci" index="11" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="11" port="0x1a"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x2"/>
    </controller>
    <controller type="pci" index="12" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="12" port="0x1b"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x3"/>
    </controller>
    <controller type="pci" index="13" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="13" port="0x1c"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x4"/>
    </controller>
    <controller type="pci" index="14" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="14" port="0x1d"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x5"/>
    </controller>
    <controller type="sata" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x1f" function="0x2"/>
    </controller>
    <interface type="network">
      <mac address="52:54:00:c3:d1:06"/>
      <source network="default"/>
      <model type="virtio"/>
      <address type="pci" domain="0x0000" bus="0x05" slot="0x00" function="0x0"/>
    </interface>
    <input type="mouse" bus="ps2"/>
    <input type="keyboard" bus="ps2"/>
    <audio id="1" type="none"/>
    <hostdev mode="subsystem" type="pci" managed="yes">
      <source>
        <address domain="0x0000" bus="0x09" slot="0x00" function="0x0"/>
      </source>
      <address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
    </hostdev>
    <hostdev mode="subsystem" type="pci" managed="yes">
      <source>
        <address domain="0x0000" bus="0x09" slot="0x00" function="0x1"/>
      </source>
      <address type="pci" domain="0x0000" bus="0x07" slot="0x00" function="0x0"/>
    </hostdev>
    <hostdev mode="subsystem" type="usb" managed="yes">
      <source>
        <vendor id="0x046d"/>
        <product id="0xc08b"/>
      </source>
      <address type="usb" bus="0" port="3"/>
    </hostdev>
    <hostdev mode="subsystem" type="usb" managed="yes">
      <source>
        <vendor id="0x1532"/>
        <product id="0x025e"/>
      </source>
      <address type="usb" bus="0" port="4"/>
    </hostdev>
    <hostdev mode="subsystem" type="usb" managed="yes">
      <source>
        <vendor id="0x10f5"/>
        <product id="0x2154"/>
      </source>
      <address type="usb" bus="0" port="5"/>
    </hostdev>
    <memballoon model="virtio">
      <address type="pci" domain="0x0000" bus="0x04" slot="0x00" function="0x0"/>
    </memballoon>
  </devices>
</domain>
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