From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: Xen/arm: Virtual ITS command queue handling Date: Tue, 19 May 2015 15:18:05 +0100 Message-ID: <1432045085.12989.146.camel@citrix.com> References: <1431442942.8263.175.camel@citrix.com> <555239ED.2090400@citrix.com> <1431523416.8263.273.camel@citrix.com> <55535F30.7040903@citrix.com> <1431687548.8943.74.camel@citrix.com> <5555E46F.4010209@citrix.com> <1431694697.8943.119.camel@citrix.com> <5555F383.7030909@citrix.com> <1432037642.12989.106.camel@citrix.com> <555B3A5C.4090502@citrix.com> <1432042604.12989.124.camel@citrix.com> <1432043681.12989.135.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Vijay Kilari Cc: Stefano Stabellini , Prasun Kapoor , manish.jaggi@caviumnetworks.com, Julien Grall , "xen-devel@lists.xen.org" , Julien Grall , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On Tue, 2015-05-19 at 19:34 +0530, Vijay Kilari wrote: > On Tue, May 19, 2015 at 7:24 PM, Ian Campbell wrote: > > On Tue, 2015-05-19 at 14:36 +0100, Ian Campbell wrote: > >> On Tue, 2015-05-19 at 14:27 +0100, Julien Grall wrote: > >> > With the multiple vITS we would have to retrieve the number of vITS. > >> > Maybe by extending the xen_arch_domainconfig? > >> > >> I'm sure we can find a way. > >> > >> The important question is whether we want to go for a N:N vits:pits > >> mapping or 1:N. > >> > >> So far I think we are leaning (slightly?) towards the 1:N model, if we > >> can come up with a satisfactory answer for what to do with global > >> commands. > > > > Actually, Julien just mentioned NUMA which I think is a strong argument > > for the N:N model. > > > > We need to make a choice here one way or another, since it has knock on > > effects on other parts, e.g the handling of SYNC and INVALL etc. > > > > Given that N:N seems likely to be simpler from the Xen side and in any > > case doesn't preclude us moving to a 1:N model (or even a 2:N model etc) > > in the future how about we start with that? > > > > If there is agreement in taking this direction then I will adjust the > > relevant sections of the document to reflect this. > > Yes, this make Xen side simple. Most important point to discuss is > > 1) How Xen maps vITS to pITS. its0 -> vits0? The choices are basically either Xen chooses and the tools get told (or "Just Know" the result), or the tools choose and setup the mapping in Xen via hypercalls. > 2) When PCI device is assigned to DomU, how does domU choose > vITS to send commands. AFAIK, the BDF of assigned device > is different from actual BDF in DomU. AIUI this is described in the firmware tables. e.g. in DT via the msi-parent phandle on the PCI root complex or individual device. Is there an assumption here that a single PCI root bridge is associated with a single ITS block? Or can different devices on a PCI bus use different ITS blocks? Ian.