Similar configuration with Windows guests (6 total):

root@cluster-05:/var/log# virsh dumpxml guest1 |grep -A 4 '<video>'
    <video>
      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </video>

This is the first error, just after starting the first vm.

Mar 28 06:27:17 cluster-05 systemd[1]: Started Virtual Machine guest1.
Mar 28 06:27:17 cluster-05 kernel: [   21.227759] ------------[ cut here ]------------
Mar 28 06:27:17 cluster-05 kernel: [   21.227762] WARNING: CPU: 21 PID: 5027 at arch/x86/kvm/vmx/vmx.c:6336 vmx_sync_pir_to_irr+0x9f/0xc0 [kvm_intel]
Mar 28 06:27:17 cluster-05 kernel: [   21.227779] Modules linked in: vhost_net vhost vhost_iotlb tap ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter bpfilter nls_iso8859_1 dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua zfs(PO) zunicode(PO) zzstd(O) ipmi_ssif zlua(O) intel_rapl_msr zavl(PO) intel_rapl_common icp(PO) zcommon(PO) znvpair(PO) spl(O) isst_if_common skx_edac nfit x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel ast kvm crct10dif_pclmul drm_vram_helper ghash_clmulni_intel joydev drm_ttm_helper ttm rapl drm_kms_helper input_leds intel_cstate cec rc_core i2c_algo_bit efi_pstore fb_sys_fops syscopyarea sysfillrect sysimgblt mei_me ioatdma mei intel_pch_thermal dca acpi_ipmi ipmi_si ipmi_devintf ipmi_msghandler bridge acpi_pad acpi_power_meter mac_hid sch_fq_codel mii 8021q garp mrp stp llc bonding tls drm ip_tables x_tables autofs4 btrfs blake2b_generic zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid0 multipath linear
Mar 28 06:27:17 cluster-05 kernel: [   21.227848]  hid_generic usbhid hid raid1 crc32_pclmul aesni_intel crypto_simd i40e mpt3sas cryptd nvme raid_class i2c_i801 scsi_transport_sas ahci nvme_core xhci_pci i2c_smbus lpc_ich libahci xhci_pci_renesas wmi
Mar 28 06:27:17 cluster-05 kernel: [   21.227865] CPU: 21 PID: 5027 Comm: CPU 0/KVM Tainted: P           O      5.13.0-37-generic #42~20.04.1-Ubuntu
Mar 28 06:27:17 cluster-05 kernel: [   21.227868] Hardware name: Supermicro SYS-5019P-M/X11SPM-F, BIOS 3.0c 03/27/2019
Mar 28 06:27:17 cluster-05 kernel: [   21.227870] RIP: 0010:vmx_sync_pir_to_irr+0x9f/0xc0 [kvm_intel]
Mar 28 06:27:17 cluster-05 kernel: [   21.227879] Code: 83 c4 10 5b 5d c3 48 89 df e8 5d 1c 30 00 8b 93 00 03 00 00 89 45 ec 83 e2 20 85 d2 75 d2 89 c7 e8 f6 fd ff ff 8b 45 ec eb c6 <0f> 0b eb 86 f0 80 4b 39 40 8b 93 00 03 00 00 8b 45 ec 83 e2 20 eb
Mar 28 06:27:17 cluster-05 kernel: [   21.227881] RSP: 0018:ffffb6e7c1f97cf0 EFLAGS: 00010246
Mar 28 06:27:17 cluster-05 kernel: [   21.227884] RAX: 0000000000000000 RBX: ffff9cd2b0a5a640 RCX: 0000000000000006
Mar 28 06:27:17 cluster-05 kernel: [   21.227886] RDX: 00000000fffe2b98 RSI: ffffffffc0e9c509 RDI: ffff9cd2b0a5a640
Mar 28 06:27:17 cluster-05 kernel: [   21.227887] RBP: ffffb6e7c1f97d08 R08: 0000000000000400 R09: 00000000ffffffff
Mar 28 06:27:17 cluster-05 kernel: [   21.227889] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9cd2b0a5a640
Mar 28 06:27:17 cluster-05 kernel: [   21.227890] R13: 00007f62755ec140 R14: ffff9cd113f99800 R15: ffff9cd2b0a5a640
Mar 28 06:27:17 cluster-05 kernel: [   21.227892] FS:  00007f62755ed700(0000) GS:ffff9cff80c80000(0000) knlGS:0000000000000000
Mar 28 06:27:17 cluster-05 kernel: [   21.227894] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar 28 06:27:17 cluster-05 kernel: [   21.227896] CR2: 00007f6278c1b001 CR3: 00000002a5ba6006 CR4: 00000000007726e0
Mar 28 06:27:17 cluster-05 kernel: [   21.227897] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Mar 28 06:27:17 cluster-05 kernel: [   21.227899] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Mar 28 06:27:17 cluster-05 kernel: [   21.227900] PKRU: 55555554
Mar 28 06:27:17 cluster-05 kernel: [   21.227901] Call Trace:
Mar 28 06:27:17 cluster-05 kernel: [   21.227903]  <TASK>
Mar 28 06:27:17 cluster-05 kernel: [   21.227906]  kvm_arch_vcpu_ioctl+0x8fd/0x1260 [kvm]
Mar 28 06:27:17 cluster-05 kernel: [   21.227973]  ? kvm_vcpu_ioctl+0x2ef/0x5f0 [kvm]
Mar 28 06:27:17 cluster-05 kernel: [   21.228014]  ? kfree+0xd8/0x2a0
Mar 28 06:27:17 cluster-05 kernel: [   21.228020]  ? kvm_vcpu_ioctl+0x2ef/0x5f0 [kvm]
Mar 28 06:27:17 cluster-05 kernel: [   21.228060]  kvm_vcpu_ioctl+0x3a7/0x5f0 [kvm]
Mar 28 06:27:17 cluster-05 kernel: [   21.228100]  ? __fget_light+0xce/0xf0
Mar 28 06:27:17 cluster-05 kernel: [   21.228104]  __x64_sys_ioctl+0x91/0xc0
Mar 28 06:27:17 cluster-05 kernel: [   21.228108]  do_syscall_64+0x61/0xb0
Mar 28 06:27:17 cluster-05 kernel: [   21.228111]  ? do_syscall_64+0x6e/0xb0
Mar 28 06:27:17 cluster-05 kernel: [   21.228113]  ? syscall_exit_to_user_mode+0x27/0x50
Mar 28 06:27:17 cluster-05 kernel: [   21.228116]  ? do_syscall_64+0x6e/0xb0
Mar 28 06:27:17 cluster-05 kernel: [   21.228118]  ? do_syscall_64+0x6e/0xb0
Mar 28 06:27:17 cluster-05 kernel: [   21.228119]  ? asm_exc_page_fault+0x8/0x30
Mar 28 06:27:17 cluster-05 kernel: [   21.228123]  entry_SYSCALL_64_after_hwframe+0x44/0xae
Mar 28 06:27:17 cluster-05 kernel: [   21.228127] RIP: 0033:0x7f6277f453db
Mar 28 06:27:17 cluster-05 kernel: [   21.228129] Code: 0f 1e fa 48 8b 05 b5 7a 0d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 85 7a 0d 00 f7 d8 64 89 01 48
Mar 28 06:27:17 cluster-05 kernel: [   21.228132] RSP: 002b:00007f62755ec098 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
Mar 28 06:27:17 cluster-05 kernel: [   21.228134] RAX: ffffffffffffffda RBX: 000000008400ae8e RCX: 00007f6277f453db
Mar 28 06:27:17 cluster-05 kernel: [   21.228136] RDX: 00007f62755ec140 RSI: ffffffff8400ae8e RDI: 000000000000001a
Mar 28 06:27:17 cluster-05 kernel: [   21.228137] RBP: 0000559e30a49c80 R08: 0000559e2f8f9d64 R09: 0000559e2f8f9fbc
Mar 28 06:27:17 cluster-05 kernel: [   21.228139] R10: 00007f626c005a40 R11: 0000000000000246 R12: 00007f62755ec140
Mar 28 06:27:17 cluster-05 kernel: [   21.228140] R13: 00007f62755ec570 R14: 00007ffdd070afc0 R15: 00007f62755ec880
Mar 28 06:27:17 cluster-05 kernel: [   21.228143]  </TASK>
Mar 28 06:27:17 cluster-05 kernel: [   21.228144] ---[ end trace 2c297e4bc9e0c305 ]---
Mar 28 06:27:17 cluster-05 kernel: [   21.228268] ------------[ cut here ]------------