From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42104) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aY9sI-00017J-Pr for qemu-devel@nongnu.org; Tue, 23 Feb 2016 05:07:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aY9sH-0005wn-Al for qemu-devel@nongnu.org; Tue, 23 Feb 2016 05:07:22 -0500 Date: Tue, 23 Feb 2016 21:05:04 +1100 From: David Gibson Message-ID: <20160223100504.GW2808@voom.fritz.box> References: <20160223052431.GS2808@voom.fritz.box> <20160223094026.GA21081@in.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="3wyj3Xt2kUWLNC5K" Content-Disposition: inline In-Reply-To: <20160223094026.GA21081@in.ibm.com> Subject: Re: [Qemu-devel] CPU hotplug, again List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bharata B Rao Cc: thuth@redhat.com, ehabkost@redhat.com, armbru@redhat.com, agraf@suse.de, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, pbonzini@redhat.com, imammedo@redhat.com, Andreas =?iso-8859-1?Q?F=E4rber?= --3wyj3Xt2kUWLNC5K Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 23, 2016 at 03:10:26PM +0530, Bharata B Rao wrote: > On Tue, Feb 23, 2016 at 04:24:31PM +1100, David Gibson wrote: > > Hi Andreas, > >=20 > > I've now found (with Thomas' help) your RFC series for socket/core > > based cpu hotplug on x86 > > (https://github.com/afaerber/qemu-cpu/compare/qom-cpu-x86). It seems > > sensible enough as far as it goes, but doesn't seem to address a bunch > > of the things that I was attempting to do with the cpu-package > > proposal - and which we absolutely need for cpu hotplug on Power. > >=20 > > 1) What interface do you envisage beyond cpu_add? > >=20 > > The patches I see just construct extra socket and core objects, but > > still control hotplug (for x86) through the cpu_add interface. That > > interface is absolutely unusable on Power, since it operates on a > > per-thread basis, whereas the PAPR guest<->host interfaces can only > > communicate information at a per-core granularity. > >=20 > > 2) When hotplugging at core or socket granularity, where would the > > code to construct the individual thread objects sit? > >=20 > > Your series has the construction done in both the machine init path > > and the hotplug path. The latter works because hotplug occurs at > > thread granularity. If we're hotplugging at core or socket > > granularity what would do the construct? The core/socket object > > itself (in instance_init? in realize?); the hotplug handler? > > something else? > >=20 > > 3) How does the management layer determine what is pluggable? > >=20 > > Both the number of pluggable slots, and what it will need to do to > > populate them. > >=20 > > 4) How do we enforce that toplogies illegal for the platform can't be > > constructed? >=20 > 5) QOM-links >=20 > Andreas, You have often talked about setting up links from machine object > to the CPU objects. Would the below code correctly capture that idea of > yours ? >=20 > #define SPAPR_MACHINE_CPU_CORE_PROP "core" >=20 > /* MachineClass.init for sPAPR */ > static void ppc_spapr_init(MachineState *machine) > { > sPAPRMachineState *spapr =3D SPAPR_MACHINE(machine); > int spapr_smp_cores =3D smp_cpus / smp_threads; > int spapr_max_cores =3D max_cpus / smp_threads; >=20 > ... > for (i =3D 0; i < spapr_max_cores; i++) { > Object *obj =3D object_new(TYPE_SPAPR_CPU_CORE); > sPAPRCPUCore *core =3D SPAPR_CPU_CORE(obj); > char name[32]; >=20 > snprintf(name, sizeof(name), "%s[%d]", SPAPR_MACHINE_CPU_CORE_PRO= P, i); >=20 > /* > * Create links from machine objects to all possible cores. > */ > object_property_add_link(OBJECT(spapr), name, TYPE_SPAPR_CPU_CORE, > (Object **)&spapr->core[i], > NULL, NULL, &error_abort);=20 >=20 > /* > * Set the QOM link from machine object to core object for all > * boot time CPUs specified with -smp. For rest of the hotpluggab= le > * cores this is done from the core hotplug path. > */ > if (i < spapr_smp_cores) { > object_property_set_link(OBJECT(spapr), OBJECT(core), > SPAPR_MACHINE_CPU_CORE_PROP, &error_= abort); I hope we can at least have a helper function to both construct the core and create the links, if we can't handle the link creation in the core object itself. Having to open-code it in each machine sounds like a recipe for subtle differences in presentation between platforms, which is exactly what we want to avoid. > } > ... > } >=20 --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --3wyj3Xt2kUWLNC5K Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWzC7QAAoJEGw4ysog2bOSpwgP/ijTPUIo8B7ndLPX/k1aC5pK Chn1KOSeuQkiCC+JkkKxU4rz6Kg5UHMxa7tPjNVuSM39/5cXWQ6H0CtTM2+r8B7g drIQ1A189NnacEWpvSUMiYgzOAarzghGYENVnKk+nNf12z539rU9ns6NWU7gEnLx 9klhP0OKI68FzRXDWUN0ILlH3pfKetK1gevNL5+RT6xAGKv7+pA/CZ231HbCUWt7 buzeSTt7PfzWixReZ1cj2xHkYCSikINnp9Xiy/tMn2TnsN8Fpcxpr+xDstLgGle3 3RzgpOI0ew03VUv4KKwDbTmfJieFmkJ2g4wAHXAiZNMGt1FzXXonl1+7ah8qEcJp jJIv8mwE1QhT+dU3V7BnXV5eCT0KO7UviRyyurzHagZzYvSqAOektV2d5FHDHiwU 5Ir2dJ4F3cF97kwHlrZsO5HdF3sLlnAtgRAlv636IcSe6ef5nxDJEHjuhYi5vusf z6BGq0N1g+ixTgIk4oV6VIdNI4aZPwxBr4F/tx+jKnpqe25nbfgqTpFXXkcLO9G+ 6lOyTMQSYxNrizZPs3LSCcbCj2zSCXYLxmGEaz21w4l2cp0X/kIo+rvYR4rZuGyO 4nQ6XbGw5nJ8I+LsnLaAy4NrsLQB6bBxJ7IP7NSWD1y7nLeMTQ78zLZqHewBXwKs PLEpm9LflGriooRp8SpE =uMl6 -----END PGP SIGNATURE----- --3wyj3Xt2kUWLNC5K--