Re: [libvirt] [PATCH 9/9] qemu: Use more data for comparing CPUs

With QEMU older than 2.9.0 libvirt uses CPUID instruction to determine what CPU features are supported on the host. This was later used when checking compatibility of guest CPUs. Since QEMU 2.9.0 we ask QEMU for the host CPU data. But the two methods we use usually provide disjoint sets of CPU features because QEMU/KVM does not support all features provided by the host CPU and on the other hand it can enable some feature even if the host CPU does not support them. So if there is a domain which requires a CPU features disabled by QEMU/KVM, libvirt will refuse to start it with QEMU > 2.9.0 as its guest CPU is incompatible with the host CPU data we got from QEMU. But such domain would happily start on older QEMU (of course, the features would be missing the guest CPU). To fix this regression, we need to combine both CPU feature sets when checking guest CPU compatibility. https://bugzilla.redhat.com/show_bug.cgi?id=1439933 Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; --- src/qemu/qemu_capabilities.c | 35 +++++++++++++++++++++++++++++++++-- src/qemu/qemu_capabilities.h | 4 ++++ src/qemu/qemu_process.c | 2 +- 3 files changed, 38 insertions(+), 3 deletions(-)