From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53862) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fEPUX-000238-Rr for qemu-devel@nongnu.org; Thu, 03 May 2018 21:26:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fEPUU-0004BA-V4 for qemu-devel@nongnu.org; Thu, 03 May 2018 21:26:33 -0400 Date: Fri, 4 May 2018 10:15:27 +1000 From: David Gibson Message-ID: <20180504001527.GJ13229@umbus.fritz.box> References: <20180416085512.4011-1-bharata@linux.vnet.ibm.com> <20180417011427.GE20551@umbus.fritz.box> <20180417090909.GB3942@in.ibm.com> <20180418033344.GF2317@umbus.fritz.box> <20180503143421.30dd2b67@bahia.lan> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="D85EWoRcDXv1uhH1" Content-Disposition: inline In-Reply-To: <20180503143421.30dd2b67@bahia.lan> Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH v3] spapr: Support ibm, dynamic-memory-v2 property List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: Bharata B Rao , nfont@linux.vnet.ibm.com, mwb@linux.vnet.ibm.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org, imammedo@redhat.com --D85EWoRcDXv1uhH1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, May 03, 2018 at 02:34:21PM +0200, Greg Kurz wrote: > On Wed, 18 Apr 2018 13:33:44 +1000 > David Gibson wrote: >=20 > > On Tue, Apr 17, 2018 at 02:39:09PM +0530, Bharata B Rao wrote: > > > On Tue, Apr 17, 2018 at 11:14:27AM +1000, David Gibson wrote: =20 > > > > > static void spapr_machine_2_12_class_options(MachineClass *mc) > > > > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > > > > > index d60b7c6d7a..5e044c44af 100644 > > > > > --- a/include/hw/ppc/spapr.h > > > > > +++ b/include/hw/ppc/spapr.h > > > > > @@ -149,6 +149,7 @@ struct sPAPRMachineState { > > > > > sPAPROptionVector *ov5; /* QEMU-supported option vec= tors */ > > > > > sPAPROptionVector *ov5_cas; /* negotiated (via CAS) opti= on vectors */ > > > > > uint32_t max_compat_pvr; > > > > > + bool use_ibm_dynamic_memory_v2; =20 > > > >=20 > > > > TBH, I'm not really sure we even need to adjust this by machine typ= e. =20 > > >=20 > > > There are other similar features controlled by ov5 bits that > > > are also determined by machine type version: > > >=20 > > > Memory hotplug support -- sPAPRMachineClass.dr_lmb_enabled > > > Dedicated HP event support -- sPAPRMachineState.use_hotplug_event_sou= rce =20 > >=20 > > As for user settability the issue isn't that it's set by ov5, but what > > the effect of the feature is. Those other features alter runtime > > hypervisor behaviour and that behaviour has to remain the same across > > a migration. Therefore we have to keep the behaviour consistent for > > old machine types. > >=20 > > This feature affects only boot time behaviour. It has a similar > > effect to what a firmware update might, on real hardware. Furthermore > > the way CAS and the device tree work, this is vanishingly unlikely to > > break existing guests. > >=20 >=20 > The logic in spapr_ov5_cas_needed() assumes that pre 2.8 machine types on= ly > expose OV5_FORM1_AFFINITY and OV5_DRCONF_MEMORY to guests. Adding OV5_DRM= EM_V2 > unconditionally breaks this assumption and backward migration to pre 2.8 = QEMU > versions because they don't expect the "spapr_option_vector_ov5_cas" subs= ection. >=20 > This can cause problems in cloud environments that still have systems with > older QEMU versions, eg, hosts running ubuntu LTS 16.04.4 (QEMU 2.5) whic= h are > likely to stay around until admins could transition to some newer OS. Ah, good point. > > > Are you saying that presence of ibm,dynamic-memory-v2 probably should= n't > > > be dependent on machine type ? =20 > >=20 > > Yes, I am. > >=20 >=20 > I agree but we should also not put it in the migration stream then, like = we > already do for OV5_FORM1_AFFINITY and OV5_DRCONF_MEMORY. >=20 > I've spotted another backward migration breakage wrt old, but still > in use, QEMU versions. I'll send a series for both issues ASAP, so > that it has a chance to land in QEMU 2.11.2. Thanks. I've merged your patch for 2.13 now. --=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 --D85EWoRcDXv1uhH1 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAlrrph4ACgkQbDjKyiDZ s5K6QRAAyMp3IsMS94P99+d3EYcQSfw9/Lm6VCEZmS1ikdRQcgdlY0wZ5MS/1QeN UbcdLQhMupUUQpzhrD6K+SWE1PsxUQxihfCPLQoWJ5sCyVR6GKrrlPdR8t/m0v8b IHE9Xm00/9QG5qTFEGyvh1HIBSzLSdG95N76f2L2nUAid2lRv2ed0ClXxJgrZgeE YEsGK4bOCDNMqWohwG/vvW+ZCqP5YgOAP2L3SbtyCY5q5hnLM8Z/hqy6jciwSk8y 56c0vrDleLpQaDL7yUkiNjTijWJzr1+s41IRUM+aqurfArJIYxXYAfYfbSUjOsFM XbbxCZUJwPkrm+ly0zUK5VMPnFqofnw5svQcICI736j8/OO1eMhbCSq0lLp5B0Cj ENPO90tci8L0qWA27YphAEi6zqxWVqxx5xb09SAVQidjlH3n7M93yKUz+8N5BcD/ Ztj2CFwR2gPCg/0b5I31/JlM8AUHHQVAve4cxCqk8wp+0GvD5g5hhGwxWIvcTlR+ V5JdfQ45SiMTHmolLQX/7knwiZrHavxD3UqqlcDD9cmnJX8RR67GQO/Cjm53fGvh K7D7ot8qexpr4+H6J97paMi73AMbVg2V8qdnl1mAkFK905fqf6YXsAy+xiGgwl2+ AkTWJdnvZfrJ+5rISzZHdP4Xe54udU7SL8RdH5QsdIZ9aFDv7dA= =Rrxi -----END PGP SIGNATURE----- --D85EWoRcDXv1uhH1--