QEMU PCIe Root Port Patch
Please can the following patch be applied to QEMU (until QEMU 4.0 is bundled with unraid, as this fix is already present in master)
PCIe root ports are only exposed to VM guests as x1, which results in GPU pass-through performance degradation, and in some cases on higher end NVIDIA cards, the driver doesn't initialise some features of the card.
https://patchwork.kernel.org/cover/10683043/
Once applied, the following would be added to the VMs XML, to modify th
The custom Qemu arguments are still working. Starting with Qemu 4.0 they changed the naming to x-speed and x-width.
from the Official Changelog Qemu 4.0
PCI/PCIe
Generic PCIe root port link speed and width enhancements: Starting with the Q35 QEMU 4.0 machine type, generic pcie-root-port will default to the maximum PCIe link speed (16GT/s) and width (x32) provided by the PCIe 4.0 specification. Experimental options x-speed= and x-width= are provided for custom tuning,
