On Tue, Sep 01, 2015 at 02:39:00PM +0200, Igor Mammedov wrote:
> On Wed, 19 Aug 2015 10:08:22 -0700
> Eduardo Habkost <ehabk...@redhat.com> wrote:
>
> > The host cache information may not make sense for the guest if the VM
> > CPU topology doesn't match the host CPU topology. To make sure we won't
> > expose broken cache information to the guest, disable cache info
> > passthrough by default, and add a new "host-cache-info" property that
> > can be used to enable the old behavior for users that really need it.
> >
> > Cc: Benoît Canet <ben...@irqsave.net>
> > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> > ---
> > target-i386/cpu.c | 4 +---
> > 1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index cfb8aa7..3a71f15 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -689,7 +689,6 @@ struct X86CPUDefinition {
> > int stepping;
> > FeatureWordArray features;
> > char model_id[48];
> > - bool cache_info_passthrough;
> > };
> >
> > static X86CPUDefinition builtin_x86_defs[] = {
> > @@ -1416,6 +1415,7 @@ static X86CPUDefinition host_cpudef;
> >
> > static Property host_x86_cpu_properties[] = {
> > DEFINE_PROP_BOOL("migratable", X86CPU, migratable, true),
> > + DEFINE_PROP_BOOL("host-cache-info", X86CPU, cache_info_passthrough,
> > false),
> > DEFINE_PROP_END_OF_LIST()
> > };
> >
> > @@ -1442,7 +1442,6 @@ static void host_x86_cpu_class_init(ObjectClass *oc,
> > void *data)
> > cpu_x86_fill_model_id(host_cpudef.model_id);
> >
> > xcc->cpu_def = &host_cpudef;
> > - host_cpudef.cache_info_passthrough = true;
> >
> > /* level, xlevel, xlevel2, and the feature words are initialized on
> > * instance_init, because they require KVM to be initialized.
> > @@ -2076,7 +2075,6 @@ static void x86_cpu_load_def(X86CPU *cpu,
> > X86CPUDefinition *def, Error **errp)
> > object_property_set_int(OBJECT(cpu), def->stepping, "stepping", errp);
> > object_property_set_int(OBJECT(cpu), def->xlevel, "xlevel", errp);
> > object_property_set_int(OBJECT(cpu), def->xlevel2, "xlevel2", errp);
> > - cpu->cache_info_passthrough = def->cache_info_passthrough;
> Isn't that a guest visible change?
It is. I am not convinced we should spend time trying to make live
migration work with -cpu host unless we hear from an actual user that
depend on it, but in this case it is really simple to keep compatibility
by adding host-cache-info=on to PC_COMPAT_2_4, so I will send a new
version.
>
> > object_property_set_str(OBJECT(cpu), def->model_id, "model-id", errp);
> > for (w = 0; w < FEATURE_WORDS; w++) {
> > env->features[w] = def->features[w];
>
--
Eduardo
