On Thu, 13 Feb 2014 14:14:08 +0800 Chen Fan <chen.fan.fnst@xxxxxxxxxxxxxx> wrote: > On Tue, 2014-01-21 at 11:10 +0100, Andreas Färber wrote: > > Am 21.01.2014 10:51, schrieb Chen Fan: > > > On Tue, 2014-01-21 at 10:31 +0100, Igor Mammedov wrote: > > >> On Tue, 21 Jan 2014 15:12:45 +0800 > > >> Chen Fan <chen.fan.fnst@xxxxxxxxxxxxxx> wrote: > > >>> On Mon, 2014-01-20 at 13:29 +0100, Igor Mammedov wrote: > > >>>> On Fri, 17 Jan 2014 17:13:55 -0200 > > >>>> Eduardo Habkost <ehabkost@xxxxxxxxxx> wrote: > > >>>>> On Wed, Jan 15, 2014 at 03:37:04PM +0100, Igor Mammedov wrote: > > >>>>>> I recall there were objections to it since APIC ID contains topology > > >>>>>> information and it's not trivial for user to get it right. > > >>>>>> The last idea that was discussed to fix it was not expose APIC ID to > > >>>>>> user but rather introduce QOM hierarchy like: > > >>>>>> /machine/node/N/socket/X/core/Y/thread/Z > > >>>>>> and use it in user interface as a means to specify an arbitrary CPU > > >>>>>> and let QEMU calculate APIC ID based on this path. > > >>>>>> > > >>>>>> But nobody took on implementing it yet. > > >>>>> > > >>>>> We're taking so long to get a decent interface implemented, that part of > > >>>>> me is considering exposing the APIC ID directly like suggested before, > > >>>>> and requiring libvirt to calculate topology-aware APIC IDs[1] to > > >>>>> properly implement CPU hotplug (and possibly for other tasks). > > >>>> If you are speaking about > > >>>> 'qemu will core dump with "-smp 254, sockets=2, cores=3, threads=2"' > > >>>> http://patchwork.ozlabs.org/patch/301272/ > > >>>> bug then it's limitation of ACPI implementation, > > >>>> I'm going to refactor it to use full APIC ids instead of using bitmap, > > >>>> so that we won't ever run into issue regardless of cpu supported CPU count. > > >>>> > > >>>>> > > >>>>> Another part of me is hoping that the libvirt developers ask us to > > >>>>> please not do that, so I can use it as argument against exposing the > > >>>>> APIC IDs directly the next time we discuss this. :) > > >>>> > > >>>> why not try your /machine/node/N/socket/X/core/Y/thread/Z idea first. > > >>>> It will benefit not only cpu hotplug but also '-numa' and topology > > >>>> description in general. > > >>>> > > >>> have there been any plan/model of the idea? Need to add a new option to > > >>> qemu command? > > >> I suppose we can start with internal default implementation first. > > >> > > >> one way could be > > >> 1. let machine prebuild empty QOM tree /machine/node/N/socket/X/core/Y/thread/Z > > >> 2. add node, socket, core, thread properties to CPU and link CPU into respective > > >> link created by #1 > > >> > > > Thanks, I hope I can take some time to make some patches to implement > > > it. > > > > Please give us a few hours to reply. :) > > > > /machine/node seems too broad a term to me. > > You can't prebuild the full tree, you can only prepare the nodes. > > core[Y]/thread[Z] was previously discussed as syntax. > > > > The important part to decide on will be what is going to be child<> and > > what link<>. Has anyone played with the Intel Quark platform for > > instance? (Galileo board or upcoming Edison card) On a regular > > mainboard, we would have socket[X] as a link<x86_64-cpu>, which might > > point to a child<cpu> /machine/memory-node[W]/cpu[X]. But if we do so we > > can't reassign it to another memory node - acceptable? With Quark (or > > Qseven modules etc.) there would be a container object rather than the > > /machine itself that has a child<i386-cpu> instead of a link<i386-cpu>. > > I guess the memory nodes could still be on the /machine though. > > The other point of discussion between Anthony and me was whether core[Y] > > should be a link<> or child<>, same for thread. I believe a child<> is > > better as it enforces that unrealizing the CPU will unrealize all its > > cores and all its threads in the future. > > > > More issues may pop up when thinking about it longer than a few minutes. > > But yes, we need to start investigating this, and so far I had other > > priorities like getting the CPUState mess I created cleaned up. > Hi, Igor, Andreas, > > In addition, I want to know what way user could use to specify an > arbitrary CPU if using /machine/node/N/socket/X/core/Y/thread/Z idea? > -device qemu64,socket=X,core=Y,thread=Z? or add a new optional command > line? Definitely not another CLU option. I see a couple of options, 1. as you suggest with additional 'numa=N' so that QEMU could know where to attach a new CPU. 2. add 'parent' like option tied to link<cpu> property and specify full QOM path on CLI: -device cpufoo,parent=/machine/node[N]/socket[X]/... > Thanks, > Chen > > > > > Regards, > > Andreas > > > > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list