On Thu, Aug 23, 2018 at 06:32:41PM +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) > > The destination should have sockets=8, shouldn't it? > > 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.
Most of the incompleteness of input validation at smp_parse() can be explained by our fear of breaking existing configurations and making existing running VMs not runnable. But now we have a deprecation policy. If we're still afraid of breaking peoples' existing configurations, we should at least deprecate those configurations as soon as possible (and make QEMU at least emit a warning). -- Eduardo