On 01/16/2014 05:12 PM, CARVER, PAUL wrote:

Jumping back to an earlier part of the discussion, it occurs to me
that this has broader implications. There's some discussion going on
under the heading of Neutron with regard to PCI passthrough. I
imagine it's under Neutron because of a desire to provide passthrough
access to NICs, but given some of the activity around GPU based
computing it seems like sooner or later someone is going to try to
offer multi-tenant cloud servers with the ability to do GPU based
computing if they haven't already.

I'd expect that the situation with PCI passthrough may be a bit different, at least in the common case.

The usual scenario is to use SR-IOV to have a single physical device expose a bunch of virtual functions, and then a virtual function is passed through into a guest.

The physical function is the one with the "real" PCI config space, so as long as the host controls it then there should be minimal risk from the guests since they have limited access via the virtual functions--typically mostly just message-passing to the physical function.

Chris

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