From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58404) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dFzVR-0003xJ-M0 for qemu-devel@nongnu.org; Wed, 31 May 2017 05:01:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dFzVM-0006TG-Qa for qemu-devel@nongnu.org; Wed, 31 May 2017 05:01:29 -0400 Received: from 14.mo5.mail-out.ovh.net ([188.165.51.82]:47221) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dFzVM-0006Su-KG for qemu-devel@nongnu.org; Wed, 31 May 2017 05:01:24 -0400 Received: from player799.ha.ovh.net (b9.ovh.net [213.186.33.59]) by mo5.mail-out.ovh.net (Postfix) with ESMTP id CB20FFC53D for ; Wed, 31 May 2017 11:01:22 +0200 (CEST) Date: Wed, 31 May 2017 11:01:15 +0200 From: Greg Kurz Message-ID: <20170531110115.7d44d86e@bahia.ttt.fr.ibm.com> In-Reply-To: <20170531063321.GL12163@umbus.fritz.box> References: <20170525035132.24268-1-david@gibson.dropbear.id.au> <20170525035132.24268-12-david@gibson.dropbear.id.au> <20170529231408.43f12e95@bahia.ttt.fr.ibm.com> <20170531063321.GL12163@umbus.fritz.box> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/wcY3PYZ7JVs.J1QU65mMDiI"; protocol="application/pgp-signature" Subject: Re: [Qemu-devel] [Qemu-ppc] [PULL 11/18] pseries: Split CAS PVR negotiation out into a separate function List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: peter.maydell@linaro.org, qemu-devel@nongnu.org, sursingh@redhat.com, mdroth@linux.vnet.ibm.com, qemu-ppc@nongnu.org, sbobroff@redhat.com --Sig_/wcY3PYZ7JVs.J1QU65mMDiI Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 31 May 2017 16:33:21 +1000 David Gibson wrote: > On Mon, May 29, 2017 at 11:14:08PM +0200, Greg Kurz wrote: > > On Thu, 25 May 2017 13:51:25 +1000 > > David Gibson wrote: > > =20 > > > Guests of the qemu machine type go through a feature negotiation proc= ess > > > known as "client architecture support" (CAS) during early boot. This= does > > > a number of things, one of which is finding a CPU compatibility mode = which > > > can be supported by both guest and host. > > >=20 > > > In fact the CPU negotiation is probably the single most complex part = of the > > > CAS process, so this splits it out into a helper function. We've rec= ently > > > made some mistakes in maintaining backward compatibility for old mach= ine > > > types here. Splitting this out will also make it easier to fix this. > > >=20 > > > This also adds a possibly useful error message if the negotiation fai= ls > > > (i.e. if there isn't a CPU mode that's suitable for both guest and ho= st). > > >=20 > > > Signed-off-by: David Gibson > > > Reviewed-by: Laurent Vivier > > > Reviewed-by: Greg Kurz > > > --- =20 > >=20 > > Any reason for not seing these patches as well in this pull request ? > >=20 > > pseries: Restore PVR negotiation logic for pre-2.9 machine types > > pseries: Improve tracing of CPU compatibility negotiation =20 >=20 > Yes. After more discussion; and comparison with analogous x86 cases > that came up with Igor's NUMA cleanups, I've decided that the > behaviour here while guest visible comes under the heading of a > firmware behaviour change, which we don't typically arrange 100% > matching behaviour for. Meanwhile, I also found out more things that > suggest matching old behaviour correctly is going to be even messier > than I though. >=20 > So, I've decided that leaving the behaviour change in place is the > better course. Note that it won't affect migration (at least after > the other compat/migration fixes are merged). >=20 > I'll reconsider if we observe a real problem in the wild with it. >=20 Thanks for the detailed explanation! --Sig_/wcY3PYZ7JVs.J1QU65mMDiI Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEUEARECAAYFAlkuhlsACgkQAvw66wEB28LRRQCgpc0v1tLp8Ta3onIF2uQS5xg7 EewAmIiUYYNbju3R8v2oVgSI66TGehM= =Na2X -----END PGP SIGNATURE----- --Sig_/wcY3PYZ7JVs.J1QU65mMDiI--