On Mon, Mar 27, 2017 at 01:10:59PM +0200, Igor Mammedov wrote:
> On Fri, 24 Mar 2017 17:36:45 -0300
> Eduardo Habkost <ehabk...@redhat.com> wrote:
>
> > The existing code for "host" and "max" CPU models overrides every
> > single feature in the CPU object at realize time, even the ones
> > that were explicitly enabled or disabled by the user using
> > "feat=on" or "feat=off", while features set using +feat/-feat are
> > kept.
> >
> > This means "-cpu host,+invtsc" works as expected, while
> > "-cpu host,invtsc=on" doesn't.
> >
> > This was a known bug, already documented in a comment inside
> > x86_cpu_expand_features(). What makes this bug worse now is that
> > libvirt 3.0.0 and newer now use "feat=on|off" instead of
> > +feat/-feat when it detects a QEMU version that supports it (see
> > libvirt commit d47db7b16dd5422c7e487c8c8ee5b181a2f9cd66).
> >
> > Change the feature property getter/setter to set a
> > env->user_features field, to keep track of features that were
> > explicitly changed using QOM properties. Then make the
> > max_features code not override user features when handling "-cpu
> > host" and "-cpu max".
> >
> > This will also allow us to remove the plus_features/minus_features
> > hack in the future, but I plan to do that after 2.9.0 is
> > released.
> >
> > Reported-by: Jiri Denemark <jdene...@redhat.com>
> > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> > ---
> > target/i386/cpu.h | 2 ++
> > target/i386/cpu.c | 33 +++++++++++++++++++++------------
> > 2 files changed, 23 insertions(+), 12 deletions(-)
> >
> > diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> > index 07401ad9fe..c4602ca80d 100644
> > --- a/target/i386/cpu.h
> > +++ b/target/i386/cpu.h
> > @@ -1147,6 +1147,8 @@ typedef struct CPUX86State {
> > uint32_t cpuid_vendor3;
> > uint32_t cpuid_version;
> > FeatureWordArray features;
> > + /* Features that were explicitly enabled/disabled */
> > + FeatureWordArray user_features;
> > uint32_t cpuid_model[12];
> >
> > /* MTRRs */
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 7aa762245a..5f2addbf75 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -3373,15 +3373,20 @@ static void x86_cpu_expand_features(X86CPU *cpu,
> > Error **errp)
> > GList *l;
> > Error *local_err = NULL;
> >
> > - /*TODO: cpu->max_features incorrectly overwrites features
> > - * set using "feat=on|off". Once we fix this, we can convert
> > + /*TODO: Now cpu->max_features doesn't overwrite features
> > + * set using QOM properties, and we can convert
> > * plus_features & minus_features to global properties
> > * inside x86_cpu_parse_featurestr() too.
> > */
> > if (cpu->max_features) {
> > for (w = 0; w < FEATURE_WORDS; w++) {
> > - env->features[w] =
> > - x86_cpu_get_supported_feature_word(w, cpu->migratable);
> > + /* Override only features that weren't not set explicitly
> > + * by the user.
> s/not// or if it was intended rephrase to avoid double negation.
I will fix that, thanks for spotting it.
>
> > + */
> > + env->features[w] &= env->user_features[w];
> it probably should be assert to catch features not set via property,
> which shouldn't be there in the first place, I don't like silent
> filtering that happens here.
I wouldn't like to add an assert() so late in the 2.9 schedule.
But you are right that having anything present in
(env->features & ~env->user_features) would be a bug somewhere
else, and this line is not necessary.
>
> > + env->features[w] |=
> > + x86_cpu_get_supported_feature_word(w, cpu->migratable) &
> > + ~env->user_features[w];
> > }
> > }
> >
> > @@ -3692,15 +3697,17 @@ static void x86_cpu_unrealizefn(DeviceState *dev,
> > Error **errp)
> > }
> >
> > typedef struct BitProperty {
> > - uint32_t *ptr;
> > + FeatureWord w;
> it would be better if this refactoring and related changes
> were in a separate patch, something along lines:
> "x86/cpu: use FeatureWord instead of keeping a pointer to cpuid leaf"
I will do it in v2.
>
> > uint32_t mask;
> > } BitProperty;
> >
> > static void x86_cpu_get_bit_prop(Object *obj, Visitor *v, const char *name,
> > void *opaque, Error **errp)
> > {
> > + X86CPU *cpu = X86_CPU(obj);
> > BitProperty *fp = opaque;
> > - bool value = (*fp->ptr & fp->mask) == fp->mask;
> > + uint32_t f = cpu->env.features[fp->w];
> > + bool value = (f & fp->mask) == fp->mask;
> > visit_type_bool(v, name, &value, errp);
> > }
> >
> > @@ -3708,6 +3715,7 @@ static void x86_cpu_set_bit_prop(Object *obj, Visitor
> > *v, const char *name,
> > void *opaque, Error **errp)
> > {
> > DeviceState *dev = DEVICE(obj);
> > + X86CPU *cpu = X86_CPU(obj);
> > BitProperty *fp = opaque;
> > Error *local_err = NULL;
> > bool value;
> > @@ -3724,10 +3732,11 @@ static void x86_cpu_set_bit_prop(Object *obj,
> > Visitor *v, const char *name,
> > }
> >
> > if (value) {
> > - *fp->ptr |= fp->mask;
> > + cpu->env.features[fp->w] |= fp->mask;
> > } else {
> > - *fp->ptr &= ~fp->mask;
> > + cpu->env.features[fp->w] &= ~fp->mask;
> > }
> > + cpu->env.user_features[fp->w] |= fp->mask;
> > }
> >
> > static void x86_cpu_release_bit_prop(Object *obj, const char *name,
> > @@ -3745,7 +3754,7 @@ static void x86_cpu_release_bit_prop(Object *obj,
> > const char *name,
> > */
> > static void x86_cpu_register_bit_prop(X86CPU *cpu,
> > const char *prop_name,
> > - uint32_t *field,
> > + FeatureWord w,
> > int bitnr)
> > {
> > BitProperty *fp;
> > @@ -3755,11 +3764,11 @@ static void x86_cpu_register_bit_prop(X86CPU *cpu,
> > op = object_property_find(OBJECT(cpu), prop_name, NULL);
> > if (op) {
> > fp = op->opaque;
> > - assert(fp->ptr == field);
> > + assert(fp->w == w);
> > fp->mask |= mask;
> > } else {
> > fp = g_new0(BitProperty, 1);
> > - fp->ptr = field;
> > + fp->w = w;
> > fp->mask = mask;
> > object_property_add(OBJECT(cpu), prop_name, "bool",
> > x86_cpu_get_bit_prop,
> > @@ -3787,7 +3796,7 @@ static void x86_cpu_register_feature_bit_props(X86CPU
> > *cpu,
> > /* aliases don't use "|" delimiters anymore, they are registered
> > * manually using object_property_add_alias() */
> > assert(!strchr(name, '|'));
> > - x86_cpu_register_bit_prop(cpu, name, &cpu->env.features[w], bitnr);
> > + x86_cpu_register_bit_prop(cpu, name, w, bitnr);
> > }
> >
> > static GuestPanicInformation *x86_cpu_get_crash_info(CPUState *cs)
>
--
Eduardo
