From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55740) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dFxFa-0008Eu-9g for qemu-devel@nongnu.org; Wed, 31 May 2017 02:36:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dFxFW-0005Iz-DV for qemu-devel@nongnu.org; Wed, 31 May 2017 02:36:58 -0400 Date: Wed, 31 May 2017 16:33:21 +1000 From: David Gibson Message-ID: <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> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qo7zVO9a9OQ5oQtr" Content-Disposition: inline In-Reply-To: <20170529231408.43f12e95@bahia.ttt.fr.ibm.com> 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: Greg Kurz Cc: peter.maydell@linaro.org, qemu-devel@nongnu.org, sursingh@redhat.com, mdroth@linux.vnet.ibm.com, qemu-ppc@nongnu.org, sbobroff@redhat.com --qo7zVO9a9OQ5oQtr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 process > > known as "client architecture support" (CAS) during early boot. This d= oes > > a number of things, one of which is finding a CPU compatibility mode wh= ich > > 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 recen= tly > > made some mistakes in maintaining backward compatibility for old machine > > 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 fails > > (i.e. if there isn't a CPU mode that's suitable for both guest and host= ). > >=20 > > Signed-off-by: David Gibson > > Reviewed-by: Laurent Vivier > > Reviewed-by: Greg Kurz > > --- >=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 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. 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). I'll reconsider if we observe a real problem in the wild with it. --=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 --qo7zVO9a9OQ5oQtr Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJZLmOvAAoJEGw4ysog2bOSZT8QANhOD+2M8jTl0cxDKoAAr/AU iBfFTr+gAGNZe52D5VRCvkpBeYfOfrYM8gqWO3Fth1xcawTdkb0Vwz8ri/0aPaLb C3W+qesWA/u3dJrNfbxjRijDML0zAF859qmb6U1iKcDecwENZUzQAU0B0By2zipG utay8Ug0TQCFq1MCFkc6T2LQ10uOEt0BcL8dwL+Rd/e/EmwMu0QFNNhfZg0s4f4H 6x2R07QsCfCvA/hhK7ouQdkXQiziF9MS2VCksknHZwItnoFfLsZAFiyOufgM/ur+ dg7AOnCpkiiF4plJnHHCoen4kyF4Jfd1tS/0WrE7Kz0kVMTNnZ2M9c5/F8aQRf4V TbClRhRwTFTGOl+c8Up0agDZ/ibu0FVliJiegktKXZV/UA3aBwzlU9Cm3S7Dz4ER hJ2PvI5VAVrEYVrpybcdd4Sg+YcdJYVkmcePXNpmy0Ya3JwbAINrAU24S2cLzrQ2 0Rnxs3k/3/ANOfE7Jhz4haE2i1/uLD9J6DZg4/j4sOHDcCPS6Ay1NIIuQD/bNN68 BU96UPlee4XmyLXHqaGR1AVmDdlVIv0cbDUdy376u4XRwqxldly938Sw/nF4dpud Hdhs/NfgmCmDterrDFgYftfq80jXnFd4ehyvwyxPId95cmy8QtYHl988OPkMKIjV I+qzinJ+MeRDNCnrhNqw =Pc6n -----END PGP SIGNATURE----- --qo7zVO9a9OQ5oQtr--