The current state of

VGA assignment

Status:

Works for discrete graphics cards
• AMD Radeon (HD5xxx+)
• NVIDIA GeForce (8-series+)
Requires experimental vfio-pci option
• x-vga=on
Requires working VGA arbitration
Still some device specific glitches
• BSODs with AMD Catalyst + HDMI audio
• Reset issues on some Radeon cards
• Code 43 on GeForce

Issues:

• Requires experimental vfio-pci option, x-vga=on
• Not supported by libvirt because experimental
• Experimental because...
• Requires working VGA arbitration
• Drivers don't participate (vgacon)
• Drivers lie (i915)
• Xorg DRI can't handle multiple arbitration participants

Can't we fix these?

• Drivers don't participate
• fixable
• Drivers lie
• Once upon a time...
• i915 hardware allowed control of VGA resources
• designers dropped this feature
• nobody noticed?!
• i915 continues to opt-out anyway
• But if we fix that...
• Xorg DRI can't handle multiple arbitration participants

Start with fixing Xorg

DRI wants to mmap VGA MMIO space

Possible options...

• Provide a new VGA arbiter interface allowing mmaps
• Remove the mmap requirement

But what about compatibility?

“WE DO NOT BREAK USERSPACE!”

-Linus Torvalds

VGA assignment status:

Stuck

What else could we do?

Do we really need VGA?

Secondary graphics

• Emulated VGA for VM primary display
• Assigned graphics card for secondary
Supported by NVIDIA
• Requires K-series Quadro/GRID/Tesla
• Supported in RHEL7.0
• Some reports of success with Radeon

Depends on guest driver support

Legacy-free UEFI VM

• No VGA required

No VGA arbitration required!

Problem solved?

VGA Issues:

Requires "experimental" vfio-pci option
• Not supported by libvirt because experimental
• Experimental because...
Requires working VGA arbitration
• Drivers don't participate (vgacon)
• Drivers lie (i915)
• Xorg DRI cannot handle multiple arbitration participants

No Blockers

How do UEFI?

Step 1: OVMF

OVMF Setup

    /usr/libexec/qemu-kvm ... \
        -drive if=pflash,format=raw,readonly,file=/path/to/OVMF_CODE.fd \
        -drive if=pflash,format=raw,file=/copy/of/OVMF_VARS.fd
							

    <domain type='kvm'>
      ...
      <os>
        <loader readonly='yes' type='pflash'>/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd</loader>
        <nvram template='/usr/share/edk2.git/ovmf-x64/OVMF_VARS-pure-efi.fd'/>
        ...
      </os>
    </domain>
							

Step 2: EFI graphics card ROM

PCI ROMs can support multiple images

Most newer cards already support EFI

Step 3: UEFI compatible guest

Newer versions of Linux

Windows 8, Server 2012

That's it!

Other GPU Topics

440FX vs Q35

Q35 originally recommended for VFIO-VGA

Largely FUD

• Q35 looks more like the host platform
• Some Linux drivers assume an upstream PCIe port

In reality

• Windows doesn't care
• Linux is fixable

440FX is likely the easier path for Windows guests

NVIDIA: Code 43

Driver detects KVM hypervisor, fails to initialize^*

Nvidia - "Accidental" breakage, won't fix, unsupported

We can't solve it, but we can work around it

Hide the hypervisor

    -cpu [type],kvm=off
							

    <domain type='kvm'>
      ...
      <features>
        <kvm>
          <hidden state='on'/>
        </kvm>
        ...
      </features>
    </domain>
							

^*NVIDIA driver version 338.77+

NVIDIA: Code 43 Redux

Driver detects Hyper-V extensions, fails to initialize^*

Workaround: Disable use of Hyper-V extensions

Performance hit for Windows VMs

Have we entered an arms race?

^*NVIDIA driver version 344.11

Quirks

Unresolved Issues

Radeon device resets
• Sea Island GPUs don't reset correctly
• SMC firmware issue?
• Southern Island GPUs indicate PM reset capability
• doesn't work
Radeon BSOD
• Typically resolved by avoiding audio function
• Intel Graphics support
• In progress? KvmGT?
• Host/Guest suspend
• And ponies!