On 10/14/2016 02:28 PM, Eduardo Habkost wrote: Subject line is missing a word; perhaps s/don't/don't read/
> When explicitly enabling unmigratable flags using "-cpu host" > (e.g. "-cpu host,+invtsc"), the requested feature won't be > enabled because cpu->migratable is true by default. > > This is inconsistent with all other CPU models, which don't have > the "migratable" option, making "+invtsc" work without the need > for extra options. > > This happens because x86_cpu_filter_features() uses > cpu->migratable as argument for s/as/as an/ > x86_cpu_get_supported_feature_word(). This is not useful > because: > 2) on "-cpu host" it only makes QEMU disable features that were > explicitly enabled in the command-line; > 1) on all the other CPU models, cpu->migratable is already false. > > The fix is to just use 'false' as argument to > x86_cpu_get_supported_feature_word() in > x86_cpu_filter_features(). > > Note that: > > * This won't change anything for people using using > "-cpu host" or "-cpu host,migratable=<on|off>" (with no extra > features) because the x86_cpu_get_supported_feature_word() call > on the cpu->host_features check uses cpu->migratable as > argument. > * This won't change anything for any CPU model except "host" > because they all have cpu->migratable == false (and only "host" > has the "migratable" property that allows it to be changed). > * This will only cange things for people using "-cpu host,+<feature>", s/cange/change/ > where <feature> is a non-migratable feature. The only existing > named migratable feature is "invtsc". s/migratable/non-migratable/ ? > > In other words, this change will only affect people using > "-cpu host,+invtsc" (that will now get what they asked for: the > invtsc flag will be enabled). All other use cases are unaffected. > > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> > --- > target-i386/cpu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Love the commit:patch signal-to-noise ratio :) But the lengthy explanation is vital, so keep it that way. Reviewed-by: Eric Blake <ebl...@redhat.com> -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
