RE: Backend memory object creation - query

Hi Peter, Sorry for the incomplete description of the issue, we are working on a virtualization use case and trying to automate the VM creation and management using libvirt-python. Since Libvirt is basically XML oriented, we wanted to convert the existing tested QEMU commands into Libvirt XML for VM management. Below is the QEMU command - its SRIOV based GPU pass-thru in our system with KVM hypervisor qemu-system-x86_64 \ -m 4096 \ -enable-kvm \ -cpu host \ -smp cores=6 \ -drive file=/usr/share/qemu/OVMF.fd,format=raw,if=pflash \ -drive id=ubuntu_drive,if=virtio,file=/home/ubuntu/ubuntu_1.qcow2,format=qcow2,cache=none \ -usb \ -device usb-tablet \ -device virtio-vga,max_outputs=1,blob=true \ -display gtk,gl=on \ -object memory-backend-memfd,id=mem1,size=4096M \ -machine memory-backend=mem1 \ -device vfio-pci,host=0000:00:02.2 Libvirt XML (Memory backing added) <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0' <name>ubuntu-vm-test</name <memory unit="KiB">4194304</memory <currentMemory unit="KiB">4194304</currentMemory <memoryBacking <source type='memfd'/ </memoryBacking <vcpu>6</vcpu <os <loader>/usr/share/qemu/OVMF.fd</loader <type arch="x86_64" machine="pc">hvm</type <boot dev="hd" / <boot dev="cdrom" / </os <features <acpi / <apic / </features <cpu mode='host-passthrough' </cpu <clock offset="utc" </clock <on_poweroff>destroy</on_poweroff <on_reboot>restart</on_reboot <on_crash>destroy</on_crash <devices <emulator>/usr/bin/qemu-system-x86_64</emulator <disk type="file" device="disk" <driver name="qemu" type="qcow2" / <source file="=/home/ubuntu/ubuntu_1.qcow2" / <target dev="vda" bus="virtio" / </disk <serial type="pty" <target port="0" / <target type="serial" port="0" </target <alias name="serial0" / </serial <console type="pty" <target type="serial" port="0" / <alias name="serial0" / </console <hostdev mode="subsystem" type="pci" managed="yes" <driver name='vfio'/ <source <address domain="0x0000" bus="0x00" slot="0x02" function="0x03" / </source </hostdev <video <model type='virtio' virgl='off'/ <driver name='qemu'/ </video</devices<qemu:commandline <qemu:arg value='-set'/ <qemu:arg value='device.video0.blob=false'/</qemu:commandline<qemu:commandline <qemu:arg value='-display'/ <qemu:arg value='gtk,gl=on'/ </qemu:commandline</domain When we check the Libvirt logs, we noticed that converted XML to QEMU args are almost similar to the original LC_ALL=C \ PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin \ HOME=/var/lib/libvirt/qemu/domain-7-ubuntu-vm-test \ XDG_DATA_HOME=/var/lib/libvirt/qemu/domain-7-ubuntu-vm-test/.local/share \ XDG_CACHE_HOME=/var/lib/libvirt/qemu/domain-7-ubuntu-vm-test/.cache \ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain-7-ubuntu-vm-test/.config \ DISPLAY=:1.0 \ MESA_LOADER_DRIVER_OVERRIDE=i965 \ /usr/bin/qemu-system-x86_64 \ -name guest=ubuntu-vm-test,debug-threads=on \ -S \ -object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/var/lib/libvirt/qemu/domain-7-ubuntu-vm-test/master-key.aes"}' \ -machine pc-i440fx-6.0,usb=off,dump-guest-core=off,memory-backend=pc.ram \ -accel kvm \ -cpu host,migratable=on \ -bios /usr/share/qemu/OVMF.fd \ -m 4096 \ -object '{"qom-type":"memory-backend-memfd","id":"pc.ram","x-use-canonical-path-for-ramblock-id":false,"size":4294967296}' \ -overcommit mem-lock=off \ -smp 6,sockets=6,cores=1,threads=1 \ -uuid 25e70b21-5dc9-44ff-9e7a-026ba637f521 \ -display none \ -no-user-config \ -nodefaults \ -chardev socket,id=charmonitor,fd=32,server=on,wait=off \ -mon chardev=charmonitor,id=monitor,mode=control \ -rtc base=utc \ -no-shutdown \ -boot strict=on \ -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \ -blockdev '{"driver":"file","filename":"/home/ubuntu/ubuntu_1.qcow2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \ -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"qcow2","file":"libvirt-1-storage","backing":null}' \ -device virtio-blk-pci,bus=pci.0,addr=0x3,drive=libvirt-1-format,id=virtio-disk0,bootindex=1 \ -chardev pty,id=charserial0 \ -device isa-serial,chardev=charserial0,id=serial0 \ -audiodev '{"id":"audio1","driver":"none"}' \ -device virtio-vga,id=video0,max_outputs=1,bus=pci.0,addr=0x2 \ -device vfio-pci,host=0000:00:02.3,id=hostdev0,bus=pci.0,addr=0x4 \ -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 \ -set device.video0.blob=false \ -display gtk,gl=on \ -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \ -msg timestamp=on Our goal is to have GTK window enabled using libvirt-Python API, and we are seeing below issues with the lIbvirt but same commands working thgrough QEMU args. [cid:image001.png@01D813BA.46F75A10] 2022-01-22T10:49:08.685664Z qemu-system-x86_64: egl: eglGetDisplay failed 2022-01-22T10:49:08.685792Z qemu-system-x86_64: OpenGL is not supported by the display 2022-01-22 10:49:08.688+0000: shutting down, reason=failed I assume there must be some security policies set at the Libvirt side to access the OpenGL , please help us to resolve it . Thanks, Shiv -----Original Message----- From: Peter Krempa <pkrempa(a)redhat.comSent: Thursday, January 27, 2022 3:37 PM To: M, Shivakumar <shivakumar.m(a)intel.comCc: libvirt-users(a)redhat.com; libvir-list(a)redhat.com Subject: Re: Backend memory object creation - query On Thu, Jan 27, 2022 at 04:05:19 +0000, M, Shivakumar wrote: Hi, note that there's no need to CC both libvir-list and libvirt-users maling lists. Your description is a bit vague. Do you want to use it to back the guest memory? As by itself a memory object itself is useless without being attached somewhere In case you want to configure qemu to back the default memory of the VM by a memfd: Per https://www.libvirt.org/formatdomain.html#memory-backing <domain type='kvm' ... <memoryBacking <source type='memfd'/ </memoryBacking ... </domain Results into invoking qemu with: -machine pc-i440fx-2.9,usb=off,vmport=off,dump-guest-core=off,memory-backend=pc.ram \ ... -object '{"qom-type":"memory-backend-memfd","id":"pc.ram","x-use-canonical-path-for-ramblock-id":false,"size":1048576000,"host-nodes":[0],"policy":"bind"}' \