From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33921) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V9zDN-0002a5-2X for qemu-devel@nongnu.org; Thu, 15 Aug 2013 11:12:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V9zDF-00088p-D5 for qemu-devel@nongnu.org; Thu, 15 Aug 2013 11:11:52 -0400 Message-ID: <520CEFAC.6090500@suse.de> Date: Thu, 15 Aug 2013 17:11:40 +0200 From: =?ISO-8859-1?Q?Andreas_F=E4rber?= MIME-Version: 1.0 References: <1376537732-29300-1-git-send-email-aik@ozlabs.ru> <283AA2CE-F23C-4218-B28A-3779D6BA549B@suse.de> <520C6AC6.6010708@ozlabs.ru> <25583D8C-4023-4E78-9B5E-2E3970FB301E@suse.de> <1376548221.4255.103.camel@pasglop> <87vc37qerm.fsf@codemonkey.ws> In-Reply-To: <87vc37qerm.fsf@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC PATCH] powerpc: add PVR mask support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Alexey Kardashevskiy , Alexander Graf , "qemu-devel@nongnu.org" , "qemu-ppc@nongnu.org" , Paul Mackerras Am 15.08.2013 15:12, schrieb Anthony Liguori: > Everyone is talking past each other and no one is addressing the real > problem. There are two distinct issues here: >=20 > 1) We have two ABIs that cannot be changed unless there's a very good > reason to. Alexey's original patch breaks both. The guest ABI > cannot change given a fixed command line. >=20 > IOW, the exposed PVR value for -cpu POWER7 cannot change across > versions of QEMU or when running on different hardware. This breaks > live migration and save/resume. >=20 > We also cannot break the command line interface. If the last versio= n > of QEMU supported -cpu POWER7_v2.1, then we must continue to support > that. 1a) How should -cpu 0xDEADBEEF or -cpu DEADBEEF behave. I expect it to error out as before rather than applying the same fuzz/mask that -cpu host might. That would let us implement our own fuzz logic in kvm.c, operating on a GSList of ObjectClasses to handle multiple matches. Regards, Andreas >=20 > If there's a good reason to break either of these, that's fine but > that justification needs be up front in the patch commit message. >=20 > 2) The only "-cpu" that makes sense is "-cpu host" for KVM on HV (or > whatever ya'll call it). POWER does not have the ability to > virtualize the hardware PVR value. There is a virtual PVR in the > device tree but that's orthogonal to what we think of as the VCPU (i= t > essentially means IIUC that the cpu is compatible with that PVR). >=20 > We should explicitly disallow any -cpu value when KVM on HV is > enabled other than host. >=20 > The implementation of "-cpu host" is also goofy on PPC. -cpu host > does a match on existing CPU models meaning that we have to define a > CPU model for any possible CPU we run on. This would require having > every possible CPU model implemented in QEMU which is silly. > Instead, we should have a passthrough CPU model for use with "-cpu > host" which is essentially what Alexey's patch turns -cpu POWER7 > into. --=20 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imend=F6rffer; HRB 16746 AG N=FCrnbe= rg