From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55925) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vij9l-0004cV-NQ for qemu-devel@nongnu.org; Tue, 19 Nov 2013 06:07:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Vij9d-0008Ll-92 for qemu-devel@nongnu.org; Tue, 19 Nov 2013 06:07:45 -0500 Received: from mx.ipv6.kamp.de ([2a02:248:0:51::16]:41525 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vij9c-0008LX-Ui for qemu-devel@nongnu.org; Tue, 19 Nov 2013 06:07:37 -0500 Message-ID: <528B4680.6060400@kamp.de> Date: Tue, 19 Nov 2013 12:07:44 +0100 From: Peter Lieven MIME-Version: 1.0 References: <1379694292-1601-1-git-send-email-pbonzini@redhat.com> <1379694292-1601-12-git-send-email-pbonzini@redhat.com> <528A310A.60607@dlhnet.de> <528A3422.1030701@kamp.de> <528A3C4A.4090001@redhat.com> <528B3C86.3030309@kamp.de> <528B41A5.1080504@redhat.com> In-Reply-To: <528B41A5.1080504@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PULL 11/13] target-i386: forward CPUID cache leaves when -cpu host is used List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org, Anthony Liguori , =?UTF-8?B?QmVub8OudCBDYW5ldA==?= On 19.11.2013 11:47, Paolo Bonzini wrote: > Il 19/11/2013 11:25, Peter Lieven ha scritto: >> ~/git/qemu$ x86_64-softmmu/qemu-system-x86_64 -m 2048 -drive >> if=virtio,file=iscsi://172.21.200.45/iqn.2001-05.com.equallogic:0-8a0906-9d95c510a-344001d54795289f-2012-r2-1-7-0/0,format=raw,cache=writeback,aio=native >> -smp 2,cores=2,threads=1,sockets=1 -cpu host -monitor stdio -vnc :1 >> -enable-kvm -usb -usbdevice tablet -vga cirrus -global >> virtio-blk-pci.scsi=off -serial null -parallel null -boot c > What is your host CPU's topology I tested it with 1 socket, 2 cores, 2 threads per core (my workstation) and 2 sockets, 8 cores per socket, 2 threads per thread. Both crash. > >> With just -smp 2 it works. However, have a look at my other email I >> think there is a bug in smp_parse, because -smp 2 yields >> cpus=2,cores=1,threads=1,sockets=1 whereas I think cores should >> be 2. > The code matching the comment in vl.c ("compute missing values, prefer > sockets over cores over threads") would be like "-smp > cpu=2,cores=1,threads=1,sockets=2", giving this code: > > if (cpus == 0) { > sockets = sockets > 0 ? sockets : 1; > cores = cores > 0 ? cores : 1; > threads = threads > 0 ? threads : 1; > cpus = cores * threads * sockets; > } else if (sockets == 0) { > cores = cores > 0 ? cores : 1; > threads = threads > 0 ? threads : 1; > sockets = cpus / (cores * threads); > } else if (cores == 0) { > threads = threads > 0 ? threads : 1; > cores = cpus / (sockets * threads); > } else { > threads = cpus / (sockets * cores); > } I am fine with either of the both variants, it should just be consistent ;-) > > What you suggest is cores over threads over sockets: > > if (cpus == 0) { > cores = cores > 0 ? cores : 1; > threads = threads > 0 ? threads : 1; > sockets = sockets > 0 ? sockets : 1; > cpus = cores * threads * sockets; > } else if (cores == 0) { > threads = threads > 0 ? threads : 1; > sockets = sockets > 0 ? sockets : 1; > cores = cpus / (threads * sockets); > } else if (threads == 0) { > sockets = sockets > 0 ? sockets : 1; > threads = cpus / (cores * sockets); > } else { > sockets = cpus / (cores * threads); > } > > Can you test which of these two work? But I agree it's best to disable > cache-leaf forwarding. The problem is, its broken because at least cpuid index 4 includes a hint to the number of cores and threads. I think we have to disable the cache leaf forwarding if the qemu cpu topology does not match the host topology. I also tried to fix index 4, but this alone seems to be not enough. at least in index 2 seems also to be some info about cores and threads (which is currently not there).