After passing through the PCIe card EMU 1212m to a VM (kvm/qemu) and turning the VM off, I see this in dmesg:

[ 4675.188761] snd_emu10k1 0000:05:04.0: non-passthrough IOMMU detected, widening DMA allocations
[ 4675.188874] snd_emu10k1 0000:05:04.0: emu1010: Special config.
[ 4675.189019] snd_emu10k1 0000:05:04.0: emu1010: EMU_HANA_ID = 0x3f
[ 4680.350820] snd_emu10k1 0000:05:04.0: emu1010: Hana Firmware loaded
[ 4680.350878] snd_emu10k1 0000:05:04.0: emu1010: Hana version: 1.6
[ 4680.350948] snd_emu10k1 0000:05:04.0: emu1010: Card options = 0x1
[ 4680.350977] snd_emu10k1 0000:05:04.0: emu1010: Card options = 0x1
[ 4680.351583] snd_emu10k1 0000:05:04.0: emu1010: Card options3 = 0x1
[ 4680.377334] snd_emu10k1 0000:05:04.0: Audigy2 value: Special config.
[ 4680.377972] snd_emu10k1 0000:05:04.0: EMU outputs on
[ 4680.377972] snd_emu10k1 0000:05:04.0: EMU2 inputs on
[ 4680.392669] sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:01.2/0000:02:00.0/0000:03:02.0/0000:04:00.0/0000:05:04.0/sound/card0/emu10k1-synth-0-1'
[ 4680.392672] CPU: 10 PID: 5204 Comm: libvirtd Tainted: G           OE     5.4.0-40-generic #44-Ubuntu
[ 4680.392673] Hardware name: System manufacturer System Product Name/ROG STRIX X570-E GAMING, BIOS 1409 05/12/2020
[ 4680.392674] Call Trace:
[ 4680.392681]  dump_stack+0x6d/0x9a
[ 4680.392684]  sysfs_warn_dup.cold+0x17/0x35
[ 4680.392685]  sysfs_create_dir_ns+0xb8/0xd0
[ 4680.392687]  kobject_add_internal+0xbd/0x2b0
[ 4680.392688]  kobject_add+0x7e/0xb0
[ 4680.392692]  device_add+0x132/0x6b0
[ 4680.392696]  snd_seq_device_dev_register+0x1c/0x60 [snd_seq_device]
[ 4680.392702]  __snd_device_register.part.0+0x1f/0x30 [snd]
[ 4680.392706]  snd_device_register_all+0x33/0x50 [snd]
[ 4680.392709]  snd_card_register+0x62/0x1b0 [snd]
[ 4680.392712]  ? snd_hwdep_new+0xfe/0x146 [snd_hwdep]
[ 4680.392715]  snd_emux_init_hwdep+0xa0/0xd0 [snd_emux_synth]
[ 4680.392717]  snd_emux_register+0x11a/0x190 [snd_emux_synth]
[ 4680.392719]  ? 0xffffffffc1065000
[ 4680.392721]  ? sf_sample_new+0x20/0x20 [snd_emux_synth]
[ 4680.392723]  snd_emu10k1_synth_probe+0x108/0x1a0 [snd_emu10k1_synth]
[ 4680.392725]  really_probe+0x2b3/0x3e0
[ 4680.392726]  driver_probe_device+0xbc/0x100
[ 4680.392728]  __device_attach_driver+0x71/0xd0
[ 4680.392729]  ? driver_allows_async_probing+0x50/0x50
[ 4680.392731]  bus_for_each_drv+0x84/0xd0
[ 4680.392732]  __device_attach+0xe1/0x160
[ 4680.392734]  device_initial_probe+0x13/0x20
[ 4680.392735]  bus_probe_device+0x8f/0xa0
[ 4680.392737]  device_add+0x3c7/0x6b0
[ 4680.392740]  ? __snd_device_register.part.0+0x1f/0x30 [snd]
[ 4680.392742]  snd_seq_device_dev_register+0x1c/0x60 [snd_seq_device]
[ 4680.392745]  __snd_device_register.part.0+0x1f/0x30 [snd]
[ 4680.392748]  snd_device_register_all+0x33/0x50 [snd]
[ 4680.392751]  snd_card_register+0x62/0x1b0 [snd]
[ 4680.392753]  ? snd_seq_device_new+0xd0/0x126 [snd_seq_device]
[ 4680.392758]  snd_card_emu10k1_probe+0x30f/0x400 [snd_emu10k1]
[ 4680.392761]  local_pci_probe+0x48/0x80
[ 4680.392763]  pci_device_probe+0x10f/0x1b0
[ 4680.392765]  really_probe+0x159/0x3e0
[ 4680.392766]  driver_probe_device+0xbc/0x100
[ 4680.392767]  __device_attach_driver+0x71/0xd0
[ 4680.392769]  ? driver_allows_async_probing+0x50/0x50
[ 4680.392770]  bus_for_each_drv+0x84/0xd0
[ 4680.392771]  __device_attach+0xe1/0x160
[ 4680.392773]  device_attach+0x10/0x20
[ 4680.392775]  bus_rescan_devices_helper+0x39/0x80
[ 4680.392777]  drivers_probe_store+0x36/0x60
[ 4680.392778]  bus_attr_store+0x27/0x30
[ 4680.392780]  sysfs_kf_write+0x3e/0x50
[ 4680.392782]  kernfs_fop_write+0xda/0x1b0
[ 4680.392784]  __vfs_write+0x1b/0x40
[ 4680.392785]  vfs_write+0xb9/0x1a0
[ 4680.392786]  ksys_write+0x67/0xe0
[ 4680.392788]  __x64_sys_write+0x1a/0x20
[ 4680.392790]  do_syscall_64+0x57/0x190
[ 4680.392793]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 4680.392794] RIP: 0033:0x7f52456222cf
[ 4680.392795] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 29 fd ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 2d 44 89 c7 48 89 44 24 08 e8 5c fd ff ff 48
[ 4680.392796] RSP: 002b:00007f52023615a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
[ 4680.392798] RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007f52456222cf
[ 4680.392799] RDX: 000000000000000c RSI: 00007f5230062f50 RDI: 0000000000000019
[ 4680.392800] RBP: 00007f5230062f50 R08: 0000000000000000 R09: 0000000000000000
[ 4680.392800] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000019
[ 4680.392801] R13: 0000000000000019 R14: 0000000000000000 R15: 00007f5245b3ef70
[ 4680.392803] kobject_add_internal failed for emu10k1-synth-0-1 with -EEXIST, don't try to register things with the same name in the same directory.
[ 4680.392812] snd_emu10k1_synth: probe of emu10k1-synth-0-1 failed with error -12
[ 4680.392816] BUG: kernel NULL pointer dereference, address: 0000000000000030
[ 4680.392817] #PF: supervisor write access in kernel mode
[ 4680.392818] #PF: error_code(0x0002) - not-present page
[ 4680.392819] PGD 0 P4D 0 
[ 4680.392821] Oops: 0002 [#1] SMP NOPTI
[ 4680.392823] CPU: 10 PID: 5204 Comm: libvirtd Tainted: G           OE     5.4.0-40-generic #44-Ubuntu
[ 4680.392825] Hardware name: System manufacturer System Product Name/ROG STRIX X570-E GAMING, BIOS 1409 05/12/2020
[ 4680.392827] RIP: 0010:klist_node_init+0xa/0x40
[ 4680.392829] Code: ff ff 7f 77 0f 39 c8 7f 0b f0 0f b1 0f 75 e8 48 89 56 08 c3 e9 d4 70 01 00 eb f4 0f 1f 44 00 00 48 89 f8 48 8d 56 08 48 89 f7 <48> 89 56 08 48 89 56 10 c7 46 18 01 00 00 00 48 89 06 a8 01 75 15
[ 4680.392830] RSP: 0018:ffff960542897ae0 EFLAGS: 00010282
[ 4680.392831] RAX: ffff8a8472606f00 RBX: 0000000000000028 RCX: 0000000000000000
[ 4680.392832] RDX: 0000000000000030 RSI: 0000000000000028 RDI: 0000000000000028
[ 4680.392833] RBP: ffff960542897af8 R08: 0000000000000000 R09: ffff960542897940
[ 4680.392834] R10: 0000000000000000 R11: 0000000000000001 R12: ffff8a8472606f00
[ 4680.392835] R13: ffff8a84b8c2b520 R14: 0000000000000000 R15: 0000000000000000
[ 4680.392837] FS:  00007f5202362700(0000) GS:ffff8a84bea80000(0000) knlGS:0000000000000000
[ 4680.392838] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4680.392839] CR2: 0000000000000030 CR3: 00000007c0da8000 CR4: 0000000000340ee0
[ 4680.392840] Call Trace:
[ 4680.392843]  ? klist_add_tail+0x18/0x50
[ 4680.392845]  device_add+0x3de/0x6b0
[ 4680.392848]  ? __snd_device_register.part.0+0x1f/0x30 [snd]
[ 4680.392851]  snd_seq_device_dev_register+0x1c/0x60 [snd_seq_device]
[ 4680.392854]  __snd_device_register.part.0+0x1f/0x30 [snd]
[ 4680.392857]  snd_device_register_all+0x33/0x50 [snd]
[ 4680.392861]  snd_card_register+0x62/0x1b0 [snd]
[ 4680.392863]  ? snd_seq_device_new+0xd0/0x126 [snd_seq_device]
[ 4680.392867]  snd_card_emu10k1_probe+0x30f/0x400 [snd_emu10k1]
[ 4680.392869]  local_pci_probe+0x48/0x80
[ 4680.392872]  pci_device_probe+0x10f/0x1b0
[ 4680.392873]  really_probe+0x159/0x3e0
[ 4680.392875]  driver_probe_device+0xbc/0x100
[ 4680.392877]  __device_attach_driver+0x71/0xd0
[ 4680.392878]  ? driver_allows_async_probing+0x50/0x50
[ 4680.392880]  bus_for_each_drv+0x84/0xd0
[ 4680.392882]  __device_attach+0xe1/0x160
[ 4680.392884]  device_attach+0x10/0x20
[ 4680.392886]  bus_rescan_devices_helper+0x39/0x80
[ 4680.392888]  drivers_probe_store+0x36/0x60
[ 4680.392890]  bus_attr_store+0x27/0x30
[ 4680.392891]  sysfs_kf_write+0x3e/0x50
[ 4680.392893]  kernfs_fop_write+0xda/0x1b0
[ 4680.392895]  __vfs_write+0x1b/0x40
[ 4680.392897]  vfs_write+0xb9/0x1a0
[ 4680.392898]  ksys_write+0x67/0xe0
[ 4680.392900]  __x64_sys_write+0x1a/0x20
[ 4680.392902]  do_syscall_64+0x57/0x190
[ 4680.392904]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 4680.392906] RIP: 0033:0x7f52456222cf
[ 4680.392907] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 29 fd ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 2d 44 89 c7 48 89 44 24 08 e8 5c fd ff ff 48
[ 4680.392908] RSP: 002b:00007f52023615a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
[ 4680.392909] RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007f52456222cf
[ 4680.392910] RDX: 000000000000000c RSI: 00007f5230062f50 RDI: 0000000000000019
[ 4680.392911] RBP: 00007f5230062f50 R08: 0000000000000000 R09: 0000000000000000
[ 4680.392912] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000019
[ 4680.392913] R13: 0000000000000019 R14: 0000000000000000 R15: 00007f5245b3ef70
[ 4680.392915] Modules linked in: vhost_net vhost tap rfcomm vmnet(OE) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(OE) xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp ip6table_mangle ip6table_nat iptable_mangle iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink ip6table_filter ip6_tables iptable_filter bpfilter bridge stp llc cmac algif_hash algif_skcipher af_alg bnep snd_emu10k1_synth snd_emux_synth snd_seq_midi_emul snd_seq_virmidi edac_mce_amd kvm_amd snd_hda_codec_realtek kvm snd_hda_codec_generic ledtrig_audio snd_hda_codec_hdmi snd_hda_intel snd_emu10k1 snd_intel_dspcfg snd_hda_codec snd_util_mem amdgpu(OE) snd_ac97_codec snd_hda_core snd_hwdep ac97_bus snd_pcm iwlmvm amd_iommu_v2 crct10dif_pclmul amd_sched(OE) snd_seq_midi nls_iso8859_1 snd_seq_midi_event amdttm(OE) joydev mac80211 snd_rawmidi ghash_clmulni_intel input_leds libarc4 snd_seq btusb btrtl btbcm btintel aesni_intel bluetooth amdkcl(OE) snd_seq_device crypto_simd
[ 4680.392945]  snd_timer iwlwifi cryptd eeepc_wmi snd ecdh_generic asus_wmi drm_kms_helper ecc sparse_keymap glue_helper video fb_sys_fops syscopyarea sysfillrect mxm_wmi wmi_bmof k10temp ccp cfg80211 sysimgblt soundcore mac_hid sch_fq_codel nct6775 hwmon_vid lm92 parport_pc ppdev lp parport drm ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_logitech_hidpp hid_logitech_dj uas usb_storage hid_generic usbhid hid crc32_pclmul igb i2c_algo_bit nvme i2c_piix4 dca nvme_core wmi
[ 4680.392971] CR2: 0000000000000030
[ 4680.392973] ---[ end trace ed550ca7ec98e5dc ]---
[ 4680.392975] RIP: 0010:klist_node_init+0xa/0x40
[ 4680.392977] Code: ff ff 7f 77 0f 39 c8 7f 0b f0 0f b1 0f 75 e8 48 89 56 08 c3 e9 d4 70 01 00 eb f4 0f 1f 44 00 00 48 89 f8 48 8d 56 08 48 89 f7 <48> 89 56 08 48 89 56 10 c7 46 18 01 00 00 00 48 89 06 a8 01 75 15
[ 4680.392978] RSP: 0018:ffff960542897ae0 EFLAGS: 00010282
[ 4680.392979] RAX: ffff8a8472606f00 RBX: 0000000000000028 RCX: 0000000000000000
[ 4680.392980] RDX: 0000000000000030 RSI: 0000000000000028 RDI: 0000000000000028
[ 4680.392981] RBP: ffff960542897af8 R08: 0000000000000000 R09: ffff960542897940
[ 4680.392982] R10: 0000000000000000 R11: 0000000000000001 R12: ffff8a8472606f00
[ 4680.392983] R13: ffff8a84b8c2b520 R14: 0000000000000000 R15: 0000000000000000
[ 4680.392984] FS:  00007f5202362700(0000) GS:ffff8a84bea80000(0000) knlGS:0000000000000000
[ 4680.392985] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4680.392986] CR2: 0000000000000030 CR3: 00000007c0da8000 CR4: 0000000000340ee0

The card no longer works, and I have to kill the power to my PC and wait a few minutes before turning it back on for it to work again.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: libvirt-daemon 6.0.0-0ubuntu8.1
ProcVersionSignature: Ubuntu 5.4.0-40.44-generic 5.4.44
Uname: Linux 5.4.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.3
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Fri Jul  3 14:43:10 2020
InstallationDate: Installed on 2020-06-16 (17 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: libvirt
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.libvirt.nwfilter.allow-arp.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/allow-arp.xml']
modified.conffile..etc.libvirt.nwfilter.allow-dhcp-server.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/allow-dhcp-server.xml']
modified.conffile..etc.libvirt.nwfilter.allow-dhcp.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/allow-dhcp.xml']
modified.conffile..etc.libvirt.nwfilter.allow-incoming-ipv4.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/allow-incoming-ipv4.xml']
modified.conffile..etc.libvirt.nwfilter.allow-ipv4.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/allow-ipv4.xml']
modified.conffile..etc.libvirt.nwfilter.clean-traffic-gateway.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/clean-traffic-gateway.xml']
modified.conffile..etc.libvirt.nwfilter.clean-traffic.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/clean-traffic.xml']
modified.conffile..etc.libvirt.nwfilter.no-arp-ip-spoofing.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-arp-ip-spoofing.xml']
modified.conffile..etc.libvirt.nwfilter.no-arp-mac-spoofing.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-arp-mac-spoofing.xml']
modified.conffile..etc.libvirt.nwfilter.no-arp-spoofing.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-arp-spoofing.xml']
modified.conffile..etc.libvirt.nwfilter.no-ip-multicast.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-ip-multicast.xml']
modified.conffile..etc.libvirt.nwfilter.no-ip-spoofing.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-ip-spoofing.xml']
modified.conffile..etc.libvirt.nwfilter.no-mac-broadcast.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-mac-broadcast.xml']
modified.conffile..etc.libvirt.nwfilter.no-mac-spoofing.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-mac-spoofing.xml']
modified.conffile..etc.libvirt.nwfilter.no-other-l2-traffic.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-other-l2-traffic.xml']
modified.conffile..etc.libvirt.nwfilter.no-other-rarp-traffic.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/no-other-rarp-traffic.xml']
modified.conffile..etc.libvirt.nwfilter.qemu-announce-self-rarp.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/qemu-announce-self-rarp.xml']
modified.conffile..etc.libvirt.nwfilter.qemu-announce-self.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/nwfilter/qemu-announce-self.xml']
modified.conffile..etc.libvirt.qemu.conf: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/qemu.conf']
modified.conffile..etc.libvirt.qemu.networks.default.xml: [inaccessible: [Errno 13] Permission denied: '/etc/libvirt/qemu/networks/default.xml']