Merged Drivers

The following page will provide specifications and details on the current state of host DRM + VFIO-Mdev drivers in support of various vendors.

Intel i915

Intel's slides mention the ability to accelerate up to '8 VMs plus DOM0'. Source: https://01.org/sites/default/files/documentation/an_introduction_to_intel_gvt-g_for_external.pdf

Intel currently supports host DRM and VFIO-Mdev/SR-IOV functionality in it's current i915 driver sources (GVT-g) and upstreaming i915 driver sources (SR-IOV).

Known Issues

1. SR-IOV functionality is undocumented in the i915 driver API documentation.
   Confirmed affected versions: *
   

   A diagram depicting i915's shared host + VFIO-Mdev driver model.

Resolved Issues

1. Multiplexing functionality requires use modified KVM and Xen hypervisors (KVMGT/XenGT).
   Confirmed affected versions: current i915 driver sources (GVT-g)
   Fixed in: upstreaming i915 driver sources (SR-IOV)

Nvidia

Known Issues

1. Power management on laptops running mediated graphics functionality may causes graphical errors when not plugged in to AC power.
   Confirmed affected versions: 460.32.01, 460.73.04
   Possible mitigation: lore.kernel.org: "vfio/pci: Change the PF power state to D0 before enabling VFs"
2. VFIO-vmalloc errors may occur as a result of page collisions between host & guest on GPUs with smaller VRAM frame buffer sizes.
   Confirmed affected versions: 460.32.01, 460.73.04
3. Mdev service daemons may crash or load incorrectly requiring a service restart or reboot during host runtime.
   Confirmed affected versions: 460.32.01, 460.73.04, 510.xx.xx
4. Guest drivers fail to initialize correctly when VFIO-Mdev devices are mixed with some VFIO passthrough'd USB hubs.
   Confirmed affected versions: 460.73.01

Resolved Issues

1. Upon executing QEMU mdev device initialization for a second Mdev an IOMMU group binding error occurs in QEMU preventing the device from being brought up.
   Confirmed affected versions: 460.32.01, 460.73.04
   Fixed in: 510.xx.xx

AMDGPU

At this time AMDGPU does not currently support VFIO-Mdev functionality. It may be possible to incorporate Mdev Mode mediated device support similar to those functions in nvidia.ko and i915.ko in the Linux kernel's AMDGPU driver sources to produce a driver suitable for merged host+guest DRM for use with AMD GPU devices.

Known Issues

1. Host DRM does not work alongside guest VFIO-Mdev.
   Confirmed affected versions: *
2. The amdgpu kernel module doesn't contain hooks for guest signalling via irqfd & ioeventfd used for VFIO-mdev callbacks.
   Confirmed affected versions: *