From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40332) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a6yPs-0006X4-IQ for qemu-devel@nongnu.org; Thu, 10 Dec 2015 05:25:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a6yPo-0006Do-HC for qemu-devel@nongnu.org; Thu, 10 Dec 2015 05:25:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51317) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a6yPo-0006Cl-Bl for qemu-devel@nongnu.org; Thu, 10 Dec 2015 05:25:36 -0500 Date: Thu, 10 Dec 2015 10:25:28 +0000 From: "Daniel P. Berrange" Message-ID: <20151210102528.GB28508@redhat.com> References: <1449728144-6223-1-git-send-email-bharata@linux.vnet.ibm.com> <1449728144-6223-2-git-send-email-bharata@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1449728144-6223-2-git-send-email-bharata@linux.vnet.ibm.com> Subject: Re: [Qemu-devel] [RFC PATCH v0 1/9] vl: Don't allow CPU toplogies with partially filled cores Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bharata B Rao Cc: peter.maydell@linaro.org, ehabkost@redhat.com, agraf@suse.de, qemu-devel@nongnu.org, borntraeger@de.ibm.com, pbonzini@redhat.com, imammedo@redhat.com, afaerber@suse.de, david@gibson.dropbear.id.au On Thu, Dec 10, 2015 at 11:45:36AM +0530, Bharata B Rao wrote: > Prevent guests from booting with CPU topologies that have partially > filled CPU cores or can result in partially filled CPU cores after CPU > hotplug like > > -smp 15,sockets=1,cores=4,threads=4,maxcpus=16 or > -smp 15,sockets=1,cores=4,threads=4,maxcpus=17 or > > Signed-off-by: Bharata B Rao > --- > vl.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/vl.c b/vl.c > index 525929b..e656f53 100644 > --- a/vl.c > +++ b/vl.c > @@ -1252,6 +1252,19 @@ static void smp_parse(QemuOpts *opts) > smp_cores = cores > 0 ? cores : 1; > smp_threads = threads > 0 ? threads : 1; > > + if (smp_cpus % smp_threads) { > + error_report("cpu topology: " > + "smp_cpus (%u) should be multiple of threads (%u)", > + smp_cpus, smp_threads); > + exit(1); > + } > + > + if (max_cpus % smp_threads) { > + error_report("cpu topology: " > + "maxcpus (%u) should be multiple of threads (%u)", > + max_cpus, smp_threads); > + exit(1); > + } > } Adding this seems like it has a pretty high chance of causing regression, ie preventing previously working guests from booting with new QEMU. I know adding the check makes sense from a semantic POV, but are we willing to risk breaking people with such odd configurations ? Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|