From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Subject: Re: [PATCH]: xl: pci multi-function passthrough v2 Date: Tue, 10 Aug 2010 11:25:19 -0400 Message-ID: <20100810152518.GH3350@verge.net.au> References: <1281355239.18490.259.camel@qabil.uk.xensource.com> <20100809202703.GL17141@verge.net.au> <1281439546.18490.277.camel@qabil.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1281439546.18490.277.camel@qabil.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Gianni Tedesco Cc: Xen Devel , Ian Jackson , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org 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. > 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? > 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. > 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.