[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH]: xl: pci multi-function passthrough v2
On Tue, 2010-08-10 at 16:25 +0100, Simon Horman wrote: > On Tue, Aug 10, 2010 at 12:25:46PM +0100, Gianni Tedesco wrote: > > On Mon, 2010-08-09 at 21:27 +0100, Simon Horman wrote: > > > On Mon, Aug 09, 2010 at 01:00:39PM +0100, Gianni Tedesco wrote: > > > > Changes since last time: > > > > 1. Incorporate Stefanos feedback wrt. coding style, commenting > > > > non-obvious code and making single-function a special-case of > > > > multi-function > > > > 2. Also fix the case for passing through a single sub-function and > > > > re-mapping it as a single-function virtual device. (ie: pfunc = > > > > non-zero, vfunc = zero). Apparently needed for SR-IOV. > > > > 3. One-liner format change in xl pci-list-assignable to make it > > > > print a copy-and-pasteable BDF. > > > > 8<---------------------------------------- > > > > > > > > Implement PCI pass-through for multi-function devices. The supported BDF > > > > notation is: BB:DD.* - therefore passing-through a subset of functions > > > > or > > > > remapping the function numbers is not supported except for when passing > > > > through a single function which will be a virtual function 0. > > > > > > Is there any plan to extend this to allow for re-mapping and the like. > > > When I worked on the original multi-function support (last year) > > > this seemed to be a requirement of some people. > > > > I am glad you asked > > > > I initially planned to support this but it seemed like a nightmare: > > 1. The BDF notation practically becomes a regex language ;) > > I don't think its reasonable to say it becomes a regex language. > But I do agree that it becomes more complex. Well, for example BB:DD.0=7-7=0 is supposed to reverse the assignments.... but why? :) > > 2. For HVM, if a function 0 is not passed through then you don't > > generate an SCI interrupt for PCI hotplug. > > Isn't it sufficient to make sure that the guest sees a function 0, > regardless of what the physical function number is? Or am I missing > something? Yes that's all that's required. > > 3. I couldn't imagine a scenario where this wasn't erroneous thing to do > > I'm not sure that I understand this point. > I agree that your system should always produce a valid result. > But I think that there are other configurations that are > both valid and useful. Passing various functions in to different VM's and/or re-mapping the function numbers may produce a totally invalid configuration that isn't useful (AFAICT). That may be paranoia but I just want to be convinced that this is actually useful for something. > > But if someone can convince me that this is a worth-while thing to do > > (3) then (1) and (2) are just technical problems which can be > > overcome... > > People convinced me that it was worthwhile, but I'm not those people. Well, please put them in touch or maybe forward the relevant discussions? (off-list is OK, if the discussions are private) Like I say, I am not dead against the idea, I am just loathe to implement it until I can see what the point of it is. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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