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

On Thu, Apr 13, 2017 at 03:32:58PM +0200, Jiri Denemark wrote: > 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(-) ACK