From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: Xen/arm: Virtual ITS command queue handling Date: Tue, 19 May 2015 14:27:56 +0100 Message-ID: <555B3A5C.4090502@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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1432037642.12989.106.camel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell , Julien Grall Cc: Vijay Kilari , Stefano Stabellini , Prasun Kapoor , manish.jaggi@caviumnetworks.com, Julien Grall , "xen-devel@lists.xen.org" , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org Hi Ian, On 19/05/15 13:14, Ian Campbell wrote: > On Fri, 2015-05-15 at 14:24 +0100, Julien Grall wrote: >> Hi Ian, >> >> On 15/05/15 13:58, Ian Campbell wrote: >>>>>>>>> Therefore it is proposed that the restriction that a single vITS maps >>>>>>>>> to one pITS be retained. If a guest requires access to devices >>>>>>>>> associated with multiple pITSs then multiple vITS should be >>>>>>>>> configured. >>>>>>>> >>>>>>>> Having multiple vITS per domain brings other issues: >>>>>>>> - How do you know the number of ITS to describe in the device tree at boot? >>>>>>> >>>>>>> I'm not sure. I don't think 1 vs N is very different from the question >>>>>>> of 0 vs 1 though, somehow the tools need to know about the pITS setup. >>>>>> >>>>>> I don't see why the tools would require to know the pITS setup. >>>>> >>>>> Even with only a single vits the tools need to know if the system has 0, >>>>> 1, or more pits, to know whether to vreate a vits at all or not. >>>> >>>> In the 1 vITS solution no, it's only necessary to add a new gic define >>>> for the gic_version field in xen_arch_domainconfig. >>> >>> Would we expose a vITS to guests on a host which has no pITS at all? >> >> No, Xen will check if we can support vITS. See an example with my "GICv2 >> on GICv3" series. Obviously, we don't allow vGICv3 on GICv2. > > Did you mean to refer to "arm: Allow the user to specify the GIC > version" or some other part of that series? Yes I mean this patch. > I suppose you are proposing a new flag vits=yes|no passed as part of the > domain config which Xen can then update to indicate yes or no? Or is > there more to it than that? Could Xen not equally well expose nr_vits > back to the tools? A new flag or extending gic_version parameters (gic_version = "v3-its"). With the multiple vITS we would have to retrieve the number of vITS. Maybe by extending the xen_arch_domainconfig? Regards, -- Julien Grall