[Qemu-devel] [PATCH 0/3] Improve error message on invalid CPU topologies

[Radim Krčmář]

A not-a-bug reported that QEMU fails when cores=6,maxcpus=240,
https://bugzilla.redhat.com/show_bug.cgi?id=1159264

The error message is
  qemu-kvm: max_cpus is too large. APIC ID of last CPU is 317

Misconfiguration, but how large can maxcpus be?
There probably aren't many QEMU users with knowledge about initial APIC ID
assignment, so it would be better to prevent confusion by making the error
message more accessible.  Especially since big VMs are spreading.

Output after this patch is
  qemu-kvm: invalid CPU topology: maxcpus can't exceed 192 if cores=6 and 
threads=1

Looking for better wording ...

(The main problem of this series is benefit/code ratio.)

Radim Krčmář (3):
  target-i386: add apicid_pkg_width to topology.h
  target-i386: introduce x86_cpu_nr_apic_ids
  pc: improve error message with impossible max_cpus

 hw/i386/pc.c           | 12 +++++++-----
 target-i386/cpu.c      | 16 ++++++++++++++++
 target-i386/cpu.h      |  1 +
 target-i386/topology.h | 13 +++++++++++++
 tests/test-x86-cpuid.c |  9 +++++++++
 5 files changed, 46 insertions(+), 5 deletions(-)

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2.1.0