Performance is low on AMD settings. To improve performance set the following in BIOS

iommu=pt

https://docs.fedoraproject.org/en-US/Fedora/13/html/Virtualization_Guide/sect-Virtualization-Troubleshooting-Enabling_Intel_VT_and_AMD_V_virtualization_hardware_extensions_in_BIOS.html

https://access.redhat.com/documentation/en-us/red_hat_virtualization/4.1/html/installation_guide/appe-configuring_a_hypervisor_host_for_pci_passthrough

relevant section from the link above:

# vi /etc/default/grub
...
GRUB_CMDLINE_LINUX="nofb splash=quiet console=tty0 ... intel_iommu=on
...

  • For AMD, boot the machine, and append amd_iommu=on to the end of the GRUB_CMDLINE_LINUX line in the grub configuration file. ...

# vi /etc/default/grub
...
GRUB_CMDLINE_LINUX="nofb splash=quiet console=tty0 ... amd_iommu=on


Note
If intel_iommu=on or amd_iommu=on works, you can try replacing them with iommu=pt or amd_iommu=pt. The pt option only enables IOMMU for devices used in passthrough and will provide better host performance. However, the option may not be supported on all hardware. Revert to previous option if the pt option doesn't work for your host.

If the passthrough fails because the hardware does not support interrupt remapping, you can consider enabling the allow_unsafe_interrupts option if the virtual machines are trusted. The allow_unsafe_interrupts is not enabled by default because enabling it potentially exposes the host to MSI attacks from virtual machines. To enable the option:

# vi /etc/modprobe.d
options vfio_iommu_type1 allow_unsafe_interrupts=1
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