Re: [libvirt] [Qemu-devel] Problem setting CPU topology

On Tue, Jul 10, 2012 at 11:54:05AM +0200, Christophe Fergeau wrote: > On Sat, Jul 07, 2012 at 07:10:53PM +0300, Zeeshan Ali (Khattak) wrote: > > Hi, > > I'm trying to set exact CPU topology to qemu-kvm domains to match > > host's topology. In my case, host topology is: 1 socket, 2 cores and 2 > > threads. If I set the XML like this: > > > > <domain type='kvm'> > > .. > > <vcpu placement='static'>4</vcpu> > > <os> > > <type arch='i686' machine='pc-0.15'>hvm</type> > > <boot dev='hd'/> > > </os> > > <cpu mode='host-model'> > > <model fallback='allow'/> > > <topology sockets='1' cores='2' threads='2'/> > > </cpu> > > .. > > > > The qemu commandline launched for this domain looks like this: > > > > /usr/bin/qemu-kvm -name fedora17-2 -S -M pc-0.15 -cpu > > core2duo,+lahf_lm,+rdtscp,+aes,+popcnt,+sse4.2,+sse4.1,+pdcm,+xtpr,+cx16,+tm2,+est,+smx,+vmx,+ds_cpl,+dtes64,+pclmuldq,+pbe,+tm,+ht,+ss,+acpi,+ds > > -enable-kvm -m 1152 -smp 4,sockets=1,cores=2,threads=2 -uuid > > c573342b-2876-05b8-098e-6d5314cab062 -nodefconfig -nodefaults -chardev > > socket,id=charmonitor,path=/home/zeenix/.config/libvirt/qemu/lib/fedora17-2.monitor,server,nowait > > -mon chardev=charmonitor,id=monitor,mode=control -rtc > > base=utc,driftfix=slew -no-kvm-pit-reinjection -no-shutdown -no-acpi > > I debugged this together with Zeeshan, and the issue comes from this -no-acpi flag > which libvirt added because the domain XML was missing > <features><acpi/></features> > So in the end that was a bug in Boxes, not really a libvirt/qemu issue. > Unless libvirt/qemu should be taught that CPU topology won't work without ACPI > and complain about it? I don't think it's really impossible for any guest OS to recognize the CPU topology or boot the other CPUs without ACPI. It looks like it's just a limitation of (most?) guest OSes. If that's the case, libvirt or QEMU can't prevent the user from running a (possibly valid) configuration just because it's not very common. -- Eduardo