Re: [Xen-users] pci passthrough question. Do I need VT-D ?

["sven waeyenbergh" <sven.waeyenbergh@xxxxxxxxx>]

indeed, VT-d is needed to do pci passthrough to a HVM domain.
It is not needed for a PV domain, i have been running a mythtv domU with multiple TV-cards for ages.

but there are some requirements to get this to work.
make sure that :
- you do not load any drivers for the device on dom0 (google "pciback" for more info)
- your domU has enough memory (pci cards do use memory) and not too much, trial and error is the way to go.
- you domU kernels support PCI and the device that you're trying to passthrough
- you add the "pci" statement to your config file (ex: pci = ['04:08.0'],['04:09.0'],['06:09.0'] )
- if problems arise, you probably need to append a statement like this one to the kernel options of the domU:
      "iommu=soft swiotlb=force"
- one more caveat: some PCI cards actually are more then 1 pci device in the output of lspci.
  for example a tvcard with seperate audio device -> you need to passthrough them both
  other devices are not "dividable" for example my new quad port gigabit card is actually 4 pci devices, but i have to passthrough them 2 by 2

i have this working for tvcards, network cards, a scsi card and USB as well as serial.
but all for PV domains, i haven't tested yet with my new VT-d enabled mobo, that should be able to do this in HVM domains as well.

Greetings,
Sven

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