Re: [libvirt] [PATCH v7 1/2] vl.c deprecate incorrect CPUs topology

-smp [cpus],sockets/cores/threads[,maxcpus] should describe topology so that total number of logical CPUs [sockets * cores * threads] would be equal to [maxcpus], however historically we didn't have such check in QEMU and it is possible to start VM with an invalid topology. Deprecate invalid options combination so we can make sure that the topology VM started with is always correct in the future. Users with an invalid sockets/cores/threads/maxcpus values should fix their CLI to make sure that [sockets * cores * threads] == [maxcpus] Signed-off-by: Igor Mammedov <imammedo(a)redhat.com&gt; Reviewed-by: Andrew Jones <drjones(a)redhat.com&gt; Reviewed-by: Eduardo Habkost <ehabkost(a)redhat.com&gt; ---

+++ b/qemu-deprecated.texi @@ -139,6 +139,19 @@ The 'file' driver for drives is no longer appropriate for character or host devices and will only accept regular files (S_IFREG). The correct driver for these file types is 'host_cdrom' or 'host_device' as appropriate. +@subsection -smp (invalid topologies) (since 3.1) + +CPU topology properties should describe whole machine topology including +possible CPUs. In other words: @var{maxcpus} should be equal to +@math{@var{sockets} * @var{cores} * @var{threads}}.

+ +However, historically it was possible to start QEMU with an incorrect topology +where @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} < @var{maxcpus}}, +which could lead to an incorrect topology enumeration by the guest. +Support for invalid topologies will be removed, the user must ensure +topologies described with -smp include all possible cpus, i.e. + @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.