There is no particularly valuable log, but an error will be reported when QEMU KVM is started.
qemu unexpectedly closed the monitor: 2020-11-08T14:25:16.498798Z qemu-system-x86_64: -device vfio-pci,host=0000:2e:00.0,id=hostdev0,bus=pci.8,addr=0x0: vfio 0000:2e:00.0: group 2 is not viable
Please ensure all devices within the iommu_group are bound to their vfio bus driver.
Kernel log:
sudo dmesg | grep -i -e DMAR -e IOMMU
[ 0.000000] Command line: BOOT_IMAGE=/@/boot/vmlinuz-5.8-x86_64 root=UUID=028de0c1-3902-4ef2-98bf-441bc81f5544 rw rootflags=subvol=@ amd_iommu=on iommu=pt quiet apparmor=1 security=apparmor udev.log
_priority=3
[ 0.000000] Kernel command line: BOOT_IMAGE=/@/boot/vmlinuz-5.8-x86_64 root=UUID=028de0c1-3902-4ef2-98bf-441bc81f5544 rw rootflags=subvol=@ amd_iommu=on iommu=pt quiet apparmor=1 security=apparmor u
dev.log_priority=3
[ 0.213524] iommu: Default domain type: Passthrough (set via kernel command line)
[ 0.322664] pci 0000:00:00.2: AMD-Vi: IOMMU performance counters supported
[ 0.322717] pci 0000:00:01.0: Adding to iommu group 0
[ 0.322727] pci 0000:00:01.1: Adding to iommu group 0
[ 0.322736] pci 0000:00:01.2: Adding to iommu group 0
[ 0.322747] pci 0000:00:02.0: Adding to iommu group 1
[ 0.322769] pci 0000:00:03.0: Adding to iommu group 2
[ 0.322778] pci 0000:00:03.1: Adding to iommu group 2
[ 0.322787] pci 0000:00:03.2: Adding to iommu group 2
[ 0.322796] pci 0000:00:04.0: Adding to iommu group 3
[ 0.322806] pci 0000:00:05.0: Adding to iommu group 4
[ 0.322817] pci 0000:00:07.0: Adding to iommu group 5
[ 0.322826] pci 0000:00:07.1: Adding to iommu group 6
[ 0.322837] pci 0000:00:08.0: Adding to iommu group 7
[ 0.322846] pci 0000:00:08.1: Adding to iommu group 8
[ 0.322858] pci 0000:00:14.0: Adding to iommu group 9
[ 0.322864] pci 0000:00:14.3: Adding to iommu group 9
[ 0.322894] pci 0000:00:18.0: Adding to iommu group 10
[ 0.322901] pci 0000:00:18.1: Adding to iommu group 10
[ 0.322907] pci 0000:00:18.2: Adding to iommu group 10
[ 0.322913] pci 0000:00:18.3: Adding to iommu group 10
[ 0.322919] pci 0000:00:18.4: Adding to iommu group 10
[ 0.322925] pci 0000:00:18.5: Adding to iommu group 10
[ 0.322931] pci 0000:00:18.6: Adding to iommu group 10
[ 0.322938] pci 0000:00:18.7: Adding to iommu group 10
[ 0.322944] pci 0000:01:00.0: Adding to iommu group 0
[ 0.322950] pci 0000:20:00.0: Adding to iommu group 0
[ 0.322957] pci 0000:21:03.0: Adding to iommu group 0
[ 0.322965] pci 0000:21:04.0: Adding to iommu group 0
[ 0.322971] pci 0000:21:05.0: Adding to iommu group 0
[ 0.322977] pci 0000:21:06.0: Adding to iommu group 0
[ 0.322984] pci 0000:21:08.0: Adding to iommu group 0
[ 0.322990] pci 0000:21:09.0: Adding to iommu group 0
[ 0.322996] pci 0000:21:0a.0: Adding to iommu group 0
[ 0.323018] pci 0000:25:00.0: Adding to iommu group 0
[ 0.323039] pci 0000:26:00.0: Adding to iommu group 0
[ 0.323061] pci 0000:27:00.0: Adding to iommu group 0
[ 0.323083] pci 0000:28:00.0: Adding to iommu group 0
[ 0.323091] pci 0000:2a:00.0: Adding to iommu group 0
[ 0.323100] pci 0000:2a:00.1: Adding to iommu group 0
[ 0.323108] pci 0000:2a:00.3: Adding to iommu group 0
[ 0.323116] pci 0000:2b:00.0: Adding to iommu group 0
[ 0.323125] pci 0000:2c:00.0: Adding to iommu group 0
[ 0.323143] pci 0000:2d:00.0: Adding to iommu group 2
[ 0.323150] pci 0000:2d:00.1: Adding to iommu group 2
[ 0.323156] pci 0000:2e:00.0: Adding to iommu group 2
[ 0.323163] pci 0000:2e:00.1: Adding to iommu group 2
[ 0.323172] pci 0000:2f:00.0: Adding to iommu group 11
[ 0.323185] pci 0000:30:00.0: Adding to iommu group 12
[ 0.323197] pci 0000:30:00.3: Adding to iommu group 13
[ 0.323209] pci 0000:30:00.4: Adding to iommu group 14
[ 0.323635] pci 0000:00:00.2: AMD-Vi: Found IOMMU cap 0x40
[ 0.324134] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank).
[ 0.344745] AMD-Vi: AMD IOMMUv2 driver by Joerg Roedel <jroedel@suse.de>
I’m using 3900x, and downgrading the BIOS will fix the problem.
Ryzen5000 users are not so lucky.
And I suspect that this bug may actually affect all ryzen processors.