On 8/25/25 22:23, sven.springer--- via Users wrote:
Hi,
I am a bit lost in which parameters I need to provide to virt-install to successfully launch an SEV-SNP capable VM. I already managed to start an SEV and SEV-ES VM via virt-install, and was also able to start an SEV-SNP VM via qemu-system-x86_64 directly.
So what I am stuck with is this error message:
ERROR internal error: QEMU unexpectedly closed the monitor (vm='debian-vm-1'): 2025-08-22T17:26:25.863482Z qemu-system-x86_64: pflash with kvm requires KVM readonly memory support
when using this or variants of this command:
virt-install \ --name "$VM_NAME" \ --noautoconsole \ --graphics none \ --import \ --memory 3072 \ --vcpus 2 \ --os-variant "$OS_VARIANT" \ --network network=default,model=virtio \ --memtune hard_limit=3407872 \ --qemu-commandline='-append "root=/dev/vda1 console=ttyS0"' \ --machine confidential-guest-support=sev0,memory-backend=ram1 \ --machine=q35 \ --boot uefi,loader=/usr/share/ovmf/OVMF.amdsev.fd,loader.stateless=yes,loader.secure=no,loader.type=pflash,kernel="$VMLINUZ",initrd="$INITRD" \ --qemu-commandline='-object memory-backend-memfd,id=ram1,size=8G,share=true,prealloc=false' \ --disk bus=virtio,path="$OVERLAY_IMG",format=qcow2 \ --cloud-init user-data="$USER_DATA" \ --virt-type kvm \ --launchSecurity sev-snp,policy=0x30000,cbitpos=51,reducedPhysBits=1,kernelHashes=on \ --cpu host-passthrough \
The issue is not with the images, since with the same ones it works when going directly via qemu-system-x86_64. I notice that libvirt is converting the --boot line to -blockdev, instead of -bios which seems to be the way to go according to https://bugs.launchpad.net/ubuntu/+source/edk2/+bug/2106771 , so I tried something like --qemu-commandline='-bios /usr/share/ovmf/OVMF.amdsev.fd -kernel "$VMLINUZ"' \ but to no avail.
Did anyone manage to run a SEV-SNP VM via virt-install, or even just a libvirt-xml ? I would appreciate any tips or working xml or cli call.
I think you're hitting a bug that the following patches try to fix: https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/thread/IBI4Z... Michal