udmabuf error with libvirt + QEMU

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We are seeing an issue with udambuf, where it says “open /dev/udmabuf: No such file or directory “ even if the device exits. This issue particularly we are seeing with libvirt. When we run the QEMU args on the command line, everything works as expected.

It seems to be some permission issue when we use the Libvirt, please help us on resolving this.



Libvirt Version:  6.0.0

Host: Ubuntu 21.04  


QEMU commands:

qemu-system-x86_64 \

-enable-kvm \

-smp cores=4,threads=2,sockets=1 \

-m 4096 \

-name win-vm-0 \

-cpu host \

-drive id=windows_drive,if=virtio,file=/win10_enterprise.qcow2,format=qcow2,cache=none \

-device vfio-pci,host=0000:00:02.2 \

-device e1000,netdev=net0,mac=00:a1:00:00:00:10 \

-netdev user,id=net0,ipv6=off,hostfwd=tcp::1111-:22,hostfwd=tcp::3389-:3389 \

-monitor tcp:,server,nowait \

-rtc base=localtime \

-usb \

-device usb-tablet \

-device usb-kbd \

-device usb-mouse \

-device virtio-vga,blob=true \

-display gtk,gl=on \

-object memory-backend-memfd,id=mem1,hugetlb=off,size=4096M \

-machine memory-backend=mem1


Libvirt XML:

<?xml version="1.0"?>

<domain xmlns:qemu=http://libvirt.org/schemas/domain/qemu/1.0 type="kvm">


  <memory unit="KiB">4194304</memory>

  <currentMemory unit="KiB">4194304</currentMemory>

  <memoryBacking supported="yes">

    <source type="memfd"/>




    <type arch="x86_64" machine="pc">hvm</type>

    <boot dev="hd"/>

    <boot dev="cdrom"/>






      <relaxed state="on"/>

      <vapic state="on"/>

      <spinlocks state="on" retries="8191"/>


    <vmport state="off"/>


  <cpu mode="host-model">

    <model fallback="forbid"/>


  <clock offset="utc">







    <disk type="file" device="disk">

      <driver name="qemu" type="qcow2"/>

      <source file="/win10_enterprise.qcow2" index="1"/>


      <target dev="sda" bus="sata"/>

      <alias name="sata0-0-0"/>

      <address type="drive" controller="0" bus="0" target="0" unit="0"/>


    <interface type="bridge">

      <source bridge="br0"/>

      <model type="virtio"/>


    <serial type="pty">

      <target port="0"/>

      <target type="serial" port="0">


      <alias name="serial0"/>


    <console type="pty">

      <target type="serial" port="0"/>

      <alias name="serial0"/>


    <hostdev mode="subsystem" type="pci" managed="yes">

      <driver name="vfio"/>


        <address domain="0x0000" bus="0x00" slot="0x02" function="0x02"/>





    <qemu:arg value="-device"/>

    <qemu:arg value="virtio-vga,blob=true"/>

    <qemu:arg value="-display"/>

    <qemu:arg value="gtk,gl=on"/>

    <qemu:env name="DISPLAY" value=":1.0"/>







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