From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58272) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ft8AE-0004ed-Ei for qemu-devel@nongnu.org; Fri, 24 Aug 2018 05:13:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ft8AD-00012D-Lq for qemu-devel@nongnu.org; Fri, 24 Aug 2018 05:13:54 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39400 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ft8AD-00011m-Fh for qemu-devel@nongnu.org; Fri, 24 Aug 2018 05:13:53 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C8EC7402170A for ; Fri, 24 Aug 2018 09:13:52 +0000 (UTC) Date: Fri, 24 Aug 2018 11:13:50 +0200 From: Igor Mammedov Message-ID: <20180824111350.04d10250@redhat.com> In-Reply-To: References: <1535035877-219196-1-git-send-email-imammedo@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] vl.c: make sure maxcpus matches topology to prevent migration failure List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org, ehabkost@redhat.com, dgilbert@redhat.com On Thu, 23 Aug 2018 18:32:41 +0200 Paolo Bonzini wrote: > On 23/08/2018 16:51, Igor Mammedov wrote: > > Topology (threads*cores*sockets) must match maxcpus to be valid, > > otherwise we could start QEMU with invalid topology that throws > > a error on migration destination side, that should not be reachable: > > Source: > > -smp 8,maxcpus=64,cores=1,threads=8,sockets=1 > > // hotplug cpus upto maxcpus > > Destination: > > -smp 64,maxcpus=64,cores=1,threads=8,sockets=1 > > qemu: cpu topology: sockets (1) * cores (1) * threads (8) < smp_cpus (64) This destination CLI aren't exactly correct as well since it should've been exactly the same -smp as on source + a bunch of -device cpufoo... so we can always say go fix your CLI so it won't trigger error. > The destination should have sockets=8, shouldn't it? either that or cores=8 or cores=4,sockets=2 ... > It seems to me that, at startup, you should have cpus = s*t*c and cpus > <= maxcpus. Currently we check cpus <= s*t*c <= maxcpus, which doesn't > make much sense. I think that s*t*c should describe topology of whole machine including not yet plugged vcpus. "cpus = s*t*c" probably won't work for partially filled package case: -smp 1,cores=1,threads=8,sockets=1 cores/threads should reflect full package configuration for guest to see an expected topology. > Paolo > > > Signed-off-by: Igor Mammedov > > --- > > vl.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/vl.c b/vl.c > > index 16b913f..2b35e0c 100644 > > --- a/vl.c > > +++ b/vl.c > > @@ -1238,10 +1238,10 @@ static void smp_parse(QemuOpts *opts) > > exit(1); > > } > > > > - if (sockets * cores * threads > max_cpus) { > > + if (sockets * cores * threads != max_cpus) { > > error_report("cpu topology: " > > - "sockets (%u) * cores (%u) * threads (%u) > " > > - "maxcpus (%u)", > > + "sockets (%u) * cores (%u) * threads (%u) not equal to" > > + " maxcpus (%u)", > > sockets, cores, threads, max_cpus); > > exit(1); > > } > > >