From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48490) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQgYo-0000Tk-Dc for qemu-devel@nongnu.org; Wed, 06 Jun 2018 18:05:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQgYj-000585-Df for qemu-devel@nongnu.org; Wed, 06 Jun 2018 18:05:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50380) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fQgYj-00057W-5O for qemu-devel@nongnu.org; Wed, 06 Jun 2018 18:05:37 -0400 Date: Wed, 6 Jun 2018 19:05:31 -0300 From: Eduardo Habkost Message-ID: <20180606220531.GC7451@localhost.localdomain> References: <1528295806-90593-1-git-send-email-babu.moger@amd.com> <1528295806-90593-3-git-send-email-babu.moger@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1528295806-90593-3-git-send-email-babu.moger@amd.com> Subject: Re: [Qemu-devel] [PATCH v12 2/4] i386: Verify if topoext feature can be supported List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Babu Moger Cc: mst@redhat.com, marcel.apfelbaum@gmail.com, pbonzini@redhat.com, rth@twiddle.net, mtosatti@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, kash@tripleback.net, geoff@hostfission.com On Wed, Jun 06, 2018 at 10:36:44AM -0400, Babu Moger wrote: > topoext feature cannot be supported in certain cases > with large number of cores or threads. Add the check. > > Signed-off-by: Babu Moger > --- > target/i386/cpu.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index 86fb1a4..fc5c66d 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -509,6 +509,20 @@ static void encode_topo_cpuid8000001e(CPUState *cs, X86CPU *cpu, > } > > /* > + * Check if we can support this topology > + * Fail if number of cores are beyond the supported config > + * or nr_threads is more than 2 > + */ > +static int topology_supports_topoext(int nr_cores, int nr_threads) > +{ > + if ((nr_cores > (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET)) || > + (nr_threads > 2)) { > + return 0; > + } > + return 1; > +} > + > +/* > * Definitions of the hardcoded cache entries we expose: > * These are legacy cache values. If there is a need to change any > * of these values please use builtin_x86_defs > @@ -4941,6 +4955,19 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp) > > qemu_init_vcpu(cs); > > + /* On AMD systems, check if we can support topoext feature */ > + if (IS_AMD_CPU(env) && > + (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT)) { > + if (!topology_supports_topoext(cs->nr_cores, cs->nr_threads)) { > + /* Cannot support topoext */ > + error_setg(errp, "CPU model does not support topoext feature " > + "with number of cores(%d) and threads(%d). " > + "Please configure -smp options properly.", > + cs->nr_cores, cs->nr_threads); See error.h documentation: * Error reporting system loosely patterned after Glib's GError. * * Create an error: * error_setg(&err, "situation normal, all fouled up"); * * Create an error and add additional explanation: * error_setg(&err, "invalid quark"); * error_append_hint(&err, "Valid quarks are up, down, strange, " * "charm, top, bottom.\n"); * * Do *not* contract this to * error_setg(&err, "invalid quark\n" * "Valid quarks are up, down, strange, charm, top, bottom."); * I suggest something like this: static bool topology_supports_topoext(int nr_cores, int nr_threads, Error **errp) { if (nr_cores > (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET))) { error_setg(errp, "TOPOEXT unsupported with %d cores per socket", nr_cores); error_append_hint(errp, "TOPOEXT supports only up to %d cores per socket", (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET)); return false; } if (nr_threads > 2) { error_setg(errp, "TOPOEXT unsupported with %d threads per core", nr_threads); error_append_hint(errp, "TOPOEXT supports only up to 2 threads per core"); (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET)); return false; } return true; } static void x86_cpu_realizefn(DeviceState *dev, Error **errp) { /* ... */ if (IS_AMD_CPU(env) && (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) && !topology_supports_topoext(cs->nr_cores, cs->nr_threads, errp)) { return; } /* ... */ } -- Eduardo