Re: [Qemu-devel] [RFC 11/20] target-i386: convert 'check' and 'enforce' features into properties

[Igor Mammedov]

On Wed, 15 Aug 2012 08:39:54 -0300
Eduardo Habkost <address@hidden> wrote:

> On Tue, Aug 14, 2012 at 11:18:47PM +0200, Igor Mammedov wrote:
> > On Fri, 10 Aug 2012 12:09:04 -0300
> > Eduardo Habkost <address@hidden> wrote:
> > 
> > > On Fri, Aug 10, 2012 at 01:22:27PM +0200, Igor Mammedov wrote:
> > > > Signed-off-by: Igor Mammedov <address@hidden>
> > > > ---
> > > >  target-i386/cpu.c | 68 
> > > > ++++++++++++++++++++++++++++++++++++++++++++++---------
> > > >  1 file changed, 57 insertions(+), 11 deletions(-)
> > > > 
> > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > > > index 7734613..a154e89 100644
> > > > --- a/target-i386/cpu.c
> > > > +++ b/target-i386/cpu.c
> > > > @@ -106,8 +106,8 @@ typedef struct model_features_t {
> > > >      uint32_t cpuid;
> > > >      } model_features_t;
> > > >  
> > > > -int check_cpuid = 0;
> > > > -int enforce_cpuid = 0;
> > > > +bool check_cpuid;
> > > > +bool enforce_cpuid;
> > > >  
> > > >  void host_cpuid(uint32_t function, uint32_t count,
> > > >                  uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t 
> > > > *edx)
> > > > @@ -579,19 +579,20 @@ static int unavailable_host_feature(struct 
> > > > model_features_t *f, uint32_t mask)
> > > >   * their way to the guest.  Note: ft[].check_feat ideally should be
> > > >   * specified via a guest_def field to suppress report of extraneous 
> > > > flags.
> > > >   */
> > > > -static int check_features_against_host(x86_def_t *guest_def)
> > > > +static int check_features_against_host(X86CPU *cpu)
> > > >  {
> > > > +    CPUX86State *env = &cpu->env;
> > > >      x86_def_t host_def;
> > > >      uint32_t mask;
> > > >      int rv, i;
> > > >      struct model_features_t ft[] = {
> > > > -        {&guest_def->features, &host_def.features,
> > > > +        {&env->cpuid_features, &host_def.features,
> > > >              ~0, feature_name, 0x00000000},
> > > > -        {&guest_def->ext_features, &host_def.ext_features,
> > > > +        {&env->cpuid_ext_features, &host_def.ext_features,
> > > >              ~CPUID_EXT_HYPERVISOR, ext_feature_name, 0x00000001},
> > > > -        {&guest_def->ext2_features, &host_def.ext2_features,
> > > > +        {&env->cpuid_ext2_features, &host_def.ext2_features,
> > > >              ~PPRO_FEATURES, ext2_feature_name, 0x80000000},
> > > > -        {&guest_def->ext3_features, &host_def.ext3_features,
> > > > +        {&env->cpuid_ext3_features, &host_def.ext3_features,
> > > >              ~CPUID_EXT3_SVM, ext3_feature_name, 0x80000001}};
> > > >  
> > > >      cpu_x86_fill_host(&host_def);
> > > > @@ -1030,6 +1031,43 @@ static void x86_set_hv_vapic(Object *obj, 
> > > > Visitor *v, void *opaque,
> > > >  }
> > > >  #endif
> > > >  
> > > > +static void x86_cpuid_get_check(Object *obj, Visitor *v, void *opaque,
> > > > +                                         const char *name, Error 
> > > > **errp)
> > > > +{
> > > > +    visit_type_bool(v, &check_cpuid, name, errp);
> > > > +}
> > > > +
> > > > +static void x86_cpuid_set_check(Object *obj, Visitor *v, void *opaque,
> > > > +                                         const char *name, Error 
> > > > **errp)
> > > > +{
> > > > +    bool value;
> > > > +
> > > > +    visit_type_bool(v, &value, name, errp);
> > > > +    if (error_is_set(errp)) {
> > > > +        return;
> > > > +    }
> > > > +    check_cpuid = value;
> > > > +}
> > > > +
> > > > +static void x86_cpuid_get_enforce(Object *obj, Visitor *v, void 
> > > > *opaque,
> > > > +                                         const char *name, Error 
> > > > **errp)
> > > > +{
> > > > +    visit_type_bool(v, &enforce_cpuid, name, errp);
> > > > +}
> > > > +
> > > > +static void x86_cpuid_set_enforce(Object *obj, Visitor *v, void 
> > > > *opaque,
> > > > +                                         const char *name, Error 
> > > > **errp)
> > > > +{
> > > > +    bool value;
> > > > +
> > > > +    visit_type_bool(v, &value, name, errp);
> > > > +    if (error_is_set(errp)) {
> > > > +        return;
> > > > +    }
> > > > +    enforce_cpuid = value;
> > > > +    object_property_set_bool(obj, value, "check", errp);
> > > > +}
> > > > +
> > > >  static void cpudef_2_x86_cpu(X86CPU *cpu, x86_def_t *def, Error **errp)
> > > >  {
> > > >      CPUX86State *env = &cpu->env;
> > > > @@ -1225,10 +1263,6 @@ static int cpu_x86_find_by_name(X86CPU *cpu, 
> > > > x86_def_t *x86_cpu_def,
> > > >      x86_cpu_def->ext3_features &= ~minus_ext3_features;
> > > >      x86_cpu_def->kvm_features &= ~minus_kvm_features;
> > > >      x86_cpu_def->svm_features &= ~minus_svm_features;
> > > > -    if (check_cpuid) {
> > > > -        if (check_features_against_host(x86_cpu_def) && enforce_cpuid)
> > > > -            goto error;
> > > > -    }
> > > >      g_free(s);
> > > >      return 0;
> > > >  
> > > > @@ -1923,6 +1957,12 @@ void x86_cpu_realize(Object *obj, Error **errp)
> > > >          env->cpuid_svm_features &= TCG_SVM_FEATURES;
> > > >      }
> > > >  
> > > > +    if (check_cpuid && check_features_against_host(cpu)
> > > > +        && enforce_cpuid) {
> > > > +        error_set(errp, QERR_PERMISSION_DENIED);
> > > > +        return;
> > > > +    }
> > > > +
> > > 
> > > I just noticed that you changed behavior on patch 04/20 and now restore
> > > the behavior in this patch:
> > > 
> > > - Before patch 04/20, the feature check was being done after the
> > >   features were filtered according to the TCG support (meaning a feature
> > >   not supported by TCG will not trigger enforce/check errors).
> > before 04/20 check is done before TCG features filtering in
> > cpu_x86_find_by_name() and then later in cpu_x86_register() features are
> > TCG filtered.
> 
> Right, my mistake. The check was done on cpu_x86_find_by_name() (before
> the filtering), but for some reason I was thinking it was done much
> later. Nevermind.
> 
> > 
> > > - After patch 04/20, the check was being done _before_ the features were
> > >   filtered according to TCG support (meaning a feature not supported by
> > >   TCG would trigger enforce/check errors).
> > > - With this patch, the old behavior is restored.
> > after 04/20, it is the same as before, i.e realize is called after
> > cpu_x86_register().
> > 
> > it's by mistake that in this patch I've put check after TCG filtering, I'll
> > fix it and do check before it.
> 
> Good. I think it's a good idea to make the check before the filtering
> (and eventually, instead of checking the host CPU features directly, the
> check on TCG mode should be based on TCG_FEATURES, and the check on KVM
> mode should be based on GET_SUPPORTED_CPUID, but that's another issue).
If you are not opposed to improving checks later, I'd better re-post this
series with original behavior. Improving checks is kind of orthogonal to
moving features into properties. 

> 
> > > 
> > > I'm not sure which behavior is better. But we surely shouldn't silently
> > > move back and forth between those two modes.
> > > 
> > > IMO, checking _before_ the TCG filtering is better, as it's more
> > > predictable. it means having lots of warnings in case too-new CPU models
> > > are chosen in TCG model, but that's exactly the point.
> > > 
> > > 
> > > >  #ifndef CONFIG_USER_ONLY
> > > >      qemu_register_reset(x86_cpu_machine_reset_cb, cpu);
> > > >  #endif
> > > > @@ -1964,6 +2004,12 @@ static void x86_cpu_initfn(Object *obj)
> > > >      object_property_add(obj, "tsc-frequency", "int",
> > > >                          x86_cpuid_get_tsc_freq,
> > > >                          x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
> > > > +    object_property_add(obj, "check", "bool",
> > > > +                        x86_cpuid_get_check,
> > > > +                        x86_cpuid_set_check, NULL, NULL, NULL);
> > > > +    object_property_add(obj, "enforce", "bool",
> > > > +                        x86_cpuid_get_enforce,
> > > > +                        x86_cpuid_set_enforce, NULL, NULL, NULL);
> > > >  #if !defined(CONFIG_USER_ONLY)
> > > >      object_property_add(obj, "hv_spinlocks", "int",
> > > >                          x86_get_hv_spinlocks,
> > > > -- 
> > > > 1.7.11.2
> > > > 
> > > 
> > > -- 
> > > Eduardo
> > 
> > 
> > -- 
> > Regards,
> >   Igor
> 
> -- 
> Eduardo
> 


-- 
Regards,
  Igor