CPU model: AMD Ryzen 7 2700
KVM version: QEMU emulator version 4.1.1 (pve-qemu-kvm_4.1.1)
Host kernel version: 5.6 built from yesterday’s Ubuntu sources, configured with Proxmox settings and otherwise defaults
Kernel arch: x86_64
Guest: Windows 10 1909 Pro for Workstations 64 bit
Qemu command line: /usr/bin/kvm -id 103 -name WinDesk -chardev socket,id=qmp,path=/var/run/qemu-server/103.qmp,server,nowait -mon chardev=qmp,mode=control -chardev socket,id=qmp-event,path=/var/run/qmeventd.sock,reconnect=5 -mon chardev=qmp-event,mode=control -pidfile /var/run/qemu-server/103.pid -daemonize -smbios type=1,uuid=26d5384b-f4e6-43e9-bf07-c3746fb798f1 -drive if=pflash,unit=0,format=raw,readonly,file=/usr/share/pve-edk2-firmware//OVMF_CODE.fd -drive if=pflash,unit=1,format=raw,id=drive-efidisk0,size=131072,file=/dev/pve/vm-103-disk-1 -smp 16,sockets=1,cores=16,maxcpus=16 -nodefaults -boot menu=on,strict=on,reboot-timeout=1000,splash=/usr/share/qemu-server/bootsplash.jpg -vga none -nographic -no-hpet -cpu kvm64,enforce,hv_ipi,hv_relaxed,hv_reset,hv_runtime,hv_spinlocks=0x1fff,hv_stimer,hv_synic,hv_time,hv_vapic,hv_vendor_id=proxmox,hv_vpindex,kvm=off,+kvm_pv_eoi,+kvm_pv_unhalt,+lahf_lm,+sep -m 10240 -readconfig /usr/share/qemu-server/pve-q35-4.0.cfg -device vmgenid,guid=e52ff75c-169f-4820-9f89-6c6b4db1fcf0 -device nec-usb-xhci,id=xhci,bus=pci.1,addr=0x1b -device usb-tablet,id=tablet,bus=ehci.0,port=1 -device vfio-pci,host=0000:26:00.0,id=hostpci0.0,bus=ich9-pcie-port-1,addr=0x0.0,multifunction=on -device vfio-pci,host=0000:26:00.1,id=hostpci0.1,bus=ich9-pcie-port-1,addr=0x0.1 -device vfio-pci,host=0000:27:00.3,id=hostpci1,bus=ich9-pcie-port-2,addr=0x0 -device vfio-pci,host=0000:01:00.0,id=hostpci2,bus=ich9-pcie-port-3,addr=0x0 -device usb-host,bus=xhci.0,hostbus=1,hostport=10,id=usb0 -device usb-host,bus=xhci.0,hostbus=1,hostport=7,id=usb1 -device usb-host,bus=xhci.0,hostbus=1,hostport=3,id=usb2 -chardev socket,path=/var/run/qemu-server/103.qga,server,nowait,id=qga0 -device virtio-serial,id=qga0,bus=pci.0,addr=0x8 -device virtserialport,chardev=qga0,name=org.qemu.guest_agent.0 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 -iscsi initiator-name=iqn.1993-08.org.debian:01:f3e685b4a567 -drive if=none,id=drive-ide2,media=cdrom,aio=threads -device ide-cd,bus=ide.1,unit=0,drive=drive-ide2,id=ide2,bootindex=200 -device ahci,id=ahci0,multifunction=on,bus=pci.0,addr=0x7 -drive file=/dev/pve/vm-103-disk-0,if=none,id=drive-sata0,format=raw,cache=none,aio=native,detect-zeroes=on -device ide-hd,bus=ahci0.0,drive=drive-sata0,id=sata0,bootindex=100 -netdev type=tap,id=net0,ifname=tap103i0,script=/var/lib/qemu-server/pve-bridge,downscript=/var/lib/qemu-server/pve-bridgedown,vhost=on -device virtio-net-pci,mac=16:C7:EE:31:96:3E,netdev=net0,bus=pci.0,addr=0x12,id=net0,bootindex=300 -rtc driftfix=slew,base=localtime -machine type=q35+pve2 -global kvm-pit.lost_tick_policy=discard -machine type=q35,kernel_irqchip=on -cpu host,invtsc=on,topoext=on,monitor=off,hv-time,kvm-pv-eoi=on,hv-relaxed,hv-vapic,hv-vpindex,hv-vendor-id=proxmox,hv-crash,kvm=off,kvm-hint-dedicated=on,host-cache-info=on,l3-cache=off,x2apic=off

I did not test whether it went away when the machine was booted with no-kvm, but disabling the kernel irq chip option had no effect.

It boots if the avic option to kvm_amd is set to the default of 0.