For a couple of weeks, all UEFI machines stopped to work. When started, CPU
goes 100% (1 core) and there is no display. Now I'm using TW 20231029.

I tested installing a new machine from ISO using virt-manager wizard and the
result is the same.

I tested running the same machine directly under qemu (cutting all breaking
args) and the result is also the same. I used:

/bin/qemu-system-x86_64 -name guest=diskless-x86_64-EFI,debug-threads=on -S
-blockdev
'{"driver":"file","filename":"/usr/share/qemu/ovmf-x86_64-smm-ms-code.bin","node-name":"libvirt-pflash0-storage","auto-read-only":true,"discard":"unmap"}'
-blockdev
'{"node-name":"libvirt-pflash0-format","read-only":true,"driver":"raw","file":"libvirt-pflash0-storage"}'
-blockdev
'{"driver":"file","filename":"/tmp/a.fd","node-name":"libvirt-pflash1-storage","auto-read-only":true,"discard":"unmap"}'
-blockdev
'{"node-name":"libvirt-pflash1-format","read-only":false,"driver":"raw","file":"libvirt-pflash1-storage"}'
-machine
pc-q35-7.1,usb=off,vmport=off,smm=on,dump-guest-core=off,pflash0=libvirt-pflash0-format,pflash1=libvirt-pflash1-format,hpet=off,acpi=on
-accel kvm -cpu host,migratable=on -global
driver=cfi.pflash01,property=secure,value=on -m size=2097152k -smp
2,sockets=2,cores=1,threads=1 -uuid ede69f9b-d6ac-405b-92c0-b82cbba4650b
-no-user-config -nodefaults -rtc base=utc,driftfix=slew -global
kvm-pit.lost_tick_policy=delay -no-shutdown -global ICH9-LPC.disable_s3=1
-global ICH9-LPC.disable_s4=1 -boot menu=on,strict=on -device
'{"driver":"pcie-root-port","port":16,"chassis":1,"id":"pci.1","bus":"pcie.0","multifunction":true,"addr":"0x2"}'
-device '{"driver":"pcie-pci-bridge","id":"pci.2","bus":"pci.1","addr":"0x0"}'
-device
'{"driver":"pcie-root-port","port":17,"chassis":3,"id":"pci.3","bus":"pcie.0","addr":"0x2.0x1"}'
-device
'{"driver":"pcie-root-port","port":18,"chassis":4,"id":"pci.4","bus":"pcie.0","addr":"0x2.0x2"}'
-device
'{"driver":"pcie-root-port","port":19,"chassis":5,"id":"pci.5","bus":"pcie.0","addr":"0x2.0x3"}'
-device
'{"driver":"pcie-root-port","port":20,"chassis":6,"id":"pci.6","bus":"pcie.0","addr":"0x2.0x4"}'
-device
'{"driver":"pcie-root-port","port":21,"chassis":7,"id":"pci.7","bus":"pcie.0","addr":"0x2.0x5"}'
-device
'{"driver":"qemu-xhci","p2":15,"p3":15,"id":"usb","bus":"pci.6","addr":"0x0"}'
-device
'{"driver":"virtio-serial-pci","id":"virtio-serial0","bus":"pci.3","addr":"0x0"}'
-chardev pty,id=charserial0 -device
'{"driver":"isa-serial","chardev":"charserial0","id":"serial0","index":0}'
-chardev spicevmc,id=charchannel0,name=vdagent -device
'{"driver":"usb-tablet","id":"input0","bus":"usb.0","port":"1"}' -device
'{"driver":"virtio-vga","id":"video0","max_outputs":1,"bus":"pcie.0","addr":"0x1"}'
-device '{"driver":"intel-hda","id":"sound0","bus":"pci.2","addr":"0x2"}'
-global ICH9-LPC.noreboot=off -watchdog-action reset -chardev
spicevmc,id=charredir0,name=usbredir -device
'{"driver":"usb-redir","chardev":"charredir0","id":"redir0","bus":"usb.0","port":"2"}'
-chardev spicevmc,id=charredir1,name=usbredir -device
'{"driver":"usb-redir","chardev":"charredir1","id":"redir1","bus":"usb.0","port":"3"}'
-device
'{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.4","addr":"0x0"}'
-object '{"qom-type":"rng-random","id":"objrng0","filename":"/dev/urandom"}'
-device
'{"driver":"virtio-rng-pci","rng":"objrng0","id":"rng0","bus":"pci.7","addr":"0x0"}'
-sandbox
on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny -msg
timestamp=on -serial pty

I got this warning from my host kernel a couple of times that might be
important:

[  735.518921] x86/split lock detection: #AC: CPU 3/KVM/24708 took a split_lock
trap at address: 0x7efa5050
[  735.518926] x86/split lock detection: #AC: CPU 2/KVM/24707 took a split_lock
trap at address: 0x7efa5050
[  735.518930] x86/split lock detection: #AC: CPU 1/KVM/24706 took a split_lock
trap at address: 0x7efa5050
[  851.084245] x86/split lock detection: #AC: CPU 3/KVM/25692 took a split_lock
trap at address: 0x7efa5050
[  851.084247] x86/split lock detection: #AC: CPU 2/KVM/25691 took a split_lock
trap at address: 0x7efa5050
[  851.084248] x86/split lock detection: #AC: CPU 1/KVM/25690 took a split_lock
trap at address: 0x7efa5050
[  961.240548] x86/split lock detection: #AC: CPU 1/KVM/26038 took a split_lock
trap at address: 0x7efb5050
[ 2705.711608] x86/split lock detection: #AC: CPU 1/KVM/29276 took a split_lock
trap at address: 0x7efb5050
[ 4573.466015] x86/split lock detection: #AC: CPU 1/KVM/31559 took a split_lock
trap at address: 0x7efb5050
[ 4782.024806] x86/split lock detection: #AC: CPU 3/KVM/32386 took a split_lock
trap at address: 0x7efa5050