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Re: [Xen-API] PCI passthrough - XCP vs XenServer


  • To: Xen-api@xxxxxxxxxxxxx
  • From: Phill Edwards <philledwards@xxxxxxxxx>
  • Date: Wed, 3 Jul 2013 21:08:23 +1000
  • Delivery-date: Wed, 03 Jul 2013 11:08:36 +0000
  • List-id: User and development list for XCP and XAPI <xen-api.lists.xen.org>

> My advice is to give it a go, and report back to the list on what works (and 
> what doesn't). To request a device passthrough,
> you'll need to add an "other-config" "pci" key via the CLI, naming the bus, 
> device and function you want to passthrough. Try
> something like:
> xe vm-param-set uuid=... 
> other-config:pci=0/0000:bus:dev.fun,1/0000:bus:dev.fun2
>
> Be careful to always pass through all functions of multi-function devices 
> (some hardware doesn't like it when the functions
> are separated) and beware the code paths are different for HVM and PV.

Status report:
- I've tried to assign the 2 functions of one of the PCI devices to my
Ubuntu 12.04 VM (with MythTV installed) like this:
# xe vm-param-set other-config:pci=0/0000:05:00.0
uuid=7a1f3bcd-4b2d-4c10-5aa4-4238a48f011d
# xe vm-param-set other-config:pci=1/0000:05:00.2
uuid=7a1f3bcd-4b2d-4c10-5aa4-4238a48f011d

Whether I do it as 2 separate commands like this, or as single
combined command, I can only see one in the output of lspci on the VM:
00:00.2 Multimedia controller: Conexant Systems, Inc. CX23880/1/2/3
PCI Video and Audio Decoder [MPEG Port] (rev 05)

[ On the XCP host I see 2 lines:
05:00.0 Multimedia video controller: Conexant Systems, Inc.
CX23880/1/2/3 PCI Video and Audio Decoder (rev 05)
05:00.2 Multimedia controller: Conexant Systems, Inc. CX23880/1/2/3
PCI Video and Audio Decoder [MPEG Port] (rev 05) ]

My MythTV server can see the card, but when I try to do anything with
it (like run a channel scan) I get errors from MythTV such as "Failed
to open card", and "Could not get card info for card". This is
presumably related to the fact that only one of the functions is
showing up in lspci.

Or...perhaps the passthrough just hasn't worked and it's not been
released by the XCP host? I've noticed that I can still see the card
in lspci on the XCP host - is that expected? I read elsewhere that
you're supposed to make the device unavailable to the host by settings
in the grub conf using pciback. I haven't done any of that - am I
supposed to?

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