RE: [Xen-users] Workaround for pcifront issues

Fischer, Anna
2009-02-04T07:42:33Z

> Subject: [Xen-users] Workaround for pcifront issues
>
> I have just started to try to achieve pci passthru for a BomU so that I
> can use the host secondary ethernet interfaces directly.
>
> I am running 3.3.1 on Centos5.2 with std packages.
>
> I have detached the card from the host using pciback but have hit an
> issue with trying to get the DomU to pick it up, it wants both 01:01.0
> and 01:01.1 even though they are totally different cards.
>
> It seems that this issue has arisen somewhere between 3.1 and 3.3, to
> do
> with VT-d patches.  I am not using VT-d, is there a work around that
> doesn''t involve applying kernel or xen patches on either Do0mU or
DomU.

Yes, I have seen this as well, and I think it has to do with how the system
supports Function Level Reset (FLR), see
http://lists.xensource.com/archives/html/xen-devel/2008-07/msg00626.html. Your
cards probably are behind the same PCI bridge. If you don''t care about
the FLR functionality, then you could remove the checks for this in
tools/python/xen/xend/server/pciif.py - you just need to recompile the Xen tools
in Dom0, but no kernel changes. This is a hack though rather than a good
solution :( I am not sure if there are any other drawbacks for doing this.

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