[v3,3/3] Change other funcitons referring to feature_word_info[]

Message ID 1533909989-56115-4-git-send-email-robert.hu@linux.intel.com
State New
Headers show
Series
  • x86: QEMU side support on MSR based features
Related show

Commit Message

Robert Hoo Aug. 10, 2018, 2:06 p.m.
Add an util function feature_word_description(), which help construct the string
describing the feature word (both CPUID and MSR types).

report_unavailable_features(): add MSR_FEATURE_WORD type support.
x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
x86_cpu_get_supported_feature_word(): add MSR_FEATURE_WORD type support.
x86_cpu_adjust_feat_level(): assert the requested feature must be
CPUID_FEATURE_WORD type.

Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
---
 target/i386/cpu.c | 77 +++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 58 insertions(+), 19 deletions(-)

Comments

Eric Blake Aug. 10, 2018, 3:17 p.m. | #1
On 08/10/2018 09:06 AM, Robert Hoo wrote:

In the subject: s/funcitons/functions/

Also, it may be worth using a topic prefix (most of our commit messages 
resemble:

topic: Description of patch

to make it easier to spot patches by topic).

> Add an util function feature_word_description(), which help construct the string

s/an util/a util/
s/help/helps/

> describing the feature word (both CPUID and MSR types).
> 
> report_unavailable_features(): add MSR_FEATURE_WORD type support.
> x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
> x86_cpu_get_supported_feature_word(): add MSR_FEATURE_WORD type support.
> x86_cpu_adjust_feat_level(): assert the requested feature must be
> CPUID_FEATURE_WORD type.
> 
> Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> ---
>   target/i386/cpu.c | 77 +++++++++++++++++++++++++++++++++++++++++--------------
>   1 file changed, 58 insertions(+), 19 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index f7c70d9..21ed599 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -3024,21 +3024,51 @@ static const TypeInfo host_x86_cpu_type_info = {
>   
>   #endif
>   
> +/*
> +*caller should have input str no less than 64 byte length.
> +*/
> +#define FEATURE_WORD_DESCPTION_LEN 64

s/DESCPTION/DESCRIPTION/

> +static int feature_word_description(char str[], FeatureWordInfo *f,
> +                                            uint32_t bit)
> +{

Prone to buffer overflow if the caller doesn't pass in the length. 
Would it be better to just g_strdup_printf() into a malloc'd result 
instead of trying to snprintf()'ing into a buffer that you hope the 
caller sized large enough?

> +    int ret;
> +
> +    assert(f->type == CPUID_FEATURE_WORD ||
> +        f->type == MSR_FEATURE_WORD);
> +    switch (f->type) {
> +    case CPUID_FEATURE_WORD:
> +        {
> +            const char *reg = get_register_name_32(f->cpuid.reg);
> +            assert(reg);
> +            ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> +                "CPUID.%02XH:%s%s%s [bit %d]",
> +                f->cpuid.eax, reg,
> +                f->feat_names[bit] ? "." : "",
> +                f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> +            break;
> +        }
> +    case MSR_FEATURE_WORD:
> +        ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> +            "MSR(%xH).%s [bit %d]",
> +            f->msr.index,
> +            f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> +        break;
> +    }
Robert Hoo Aug. 14, 2018, 10:06 a.m. | #2
On Fri, 2018-08-10 at 10:17 -0500, Eric Blake wrote:
> On 08/10/2018 09:06 AM, Robert Hoo wrote:
> 
> In the subject: s/funcitons/functions/
> 
> Also, it may be worth using a topic prefix (most of our commit messages 
> resemble:
> 
> topic: Description of patch
> 
> to make it easier to spot patches by topic).
> 
> > Add an util function feature_word_description(), which help construct the string
> 
> s/an util/a util/
> s/help/helps/
> 
Thanks Eric, will fix these typos in v2.
> > describing the feature word (both CPUID and MSR types).
> > 
> > report_unavailable_features(): add MSR_FEATURE_WORD type support.
> > x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
> > x86_cpu_get_supported_feature_word(): add MSR_FEATURE_WORD type support.
> > x86_cpu_adjust_feat_level(): assert the requested feature must be
> > CPUID_FEATURE_WORD type.
> > 
> > Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> > ---
> >   target/i386/cpu.c | 77 +++++++++++++++++++++++++++++++++++++++++--------------
> >   1 file changed, 58 insertions(+), 19 deletions(-)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index f7c70d9..21ed599 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -3024,21 +3024,51 @@ static const TypeInfo host_x86_cpu_type_info = {
> >   
> >   #endif
> >   
> > +/*
> > +*caller should have input str no less than 64 byte length.
> > +*/
> > +#define FEATURE_WORD_DESCPTION_LEN 64
> 
> s/DESCPTION/DESCRIPTION/
> 
> > +static int feature_word_description(char str[], FeatureWordInfo *f,
> > +                                            uint32_t bit)
> > +{
> 
> Prone to buffer overflow if the caller doesn't pass in the length. 
> Would it be better to just g_strdup_printf() into a malloc'd result 
> instead of trying to snprintf()'ing into a buffer that you hope the 
> caller sized large enough?
> 
Oh, wasn't aware of such good util functions. Sure I'd like to use them.
Is there some web page introducing them?

Eduardo/Paolo, do you have more comments?
> > +    int ret;
> > +
> > +    assert(f->type == CPUID_FEATURE_WORD ||
> > +        f->type == MSR_FEATURE_WORD);
> > +    switch (f->type) {
> > +    case CPUID_FEATURE_WORD:
> > +        {
> > +            const char *reg = get_register_name_32(f->cpuid.reg);
> > +            assert(reg);
> > +            ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> > +                "CPUID.%02XH:%s%s%s [bit %d]",
> > +                f->cpuid.eax, reg,
> > +                f->feat_names[bit] ? "." : "",
> > +                f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> > +            break;
> > +        }
> > +    case MSR_FEATURE_WORD:
> > +        ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> > +            "MSR(%xH).%s [bit %d]",
> > +            f->msr.index,
> > +            f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> > +        break;
> > +    }
>
Eduardo Habkost Aug. 17, 2018, 1:28 p.m. | #3
On Fri, Aug 10, 2018 at 10:06:29PM +0800, Robert Hoo wrote:
> Add an util function feature_word_description(), which help construct the string
> describing the feature word (both CPUID and MSR types).
> 
> report_unavailable_features(): add MSR_FEATURE_WORD type support.
> x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
> x86_cpu_get_supported_feature_word(): add MSR_FEATURE_WORD type support.
> x86_cpu_adjust_feat_level(): assert the requested feature must be
> CPUID_FEATURE_WORD type.
> 
> Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> ---
>  target/i386/cpu.c | 77 +++++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 58 insertions(+), 19 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index f7c70d9..21ed599 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -3024,21 +3024,51 @@ static const TypeInfo host_x86_cpu_type_info = {
>  
>  #endif
>  
> +/*
> +*caller should have input str no less than 64 byte length.
> +*/
> +#define FEATURE_WORD_DESCPTION_LEN 64
> +static int feature_word_description(char str[], FeatureWordInfo *f,
> +                                            uint32_t bit)

I agree with Eric: g_strup_printf() would be much simpler here.

> +{
> +    int ret;
> +
> +    assert(f->type == CPUID_FEATURE_WORD ||
> +        f->type == MSR_FEATURE_WORD);
> +    switch (f->type) {
> +    case CPUID_FEATURE_WORD:
> +        {
> +            const char *reg = get_register_name_32(f->cpuid.reg);
> +            assert(reg);
> +            ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> +                "CPUID.%02XH:%s%s%s [bit %d]",
> +                f->cpuid.eax, reg,
> +                f->feat_names[bit] ? "." : "",
> +                f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> +            break;
> +        }
> +    case MSR_FEATURE_WORD:
> +        ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> +            "MSR(%xH).%s [bit %d]",
> +            f->msr.index,
> +            f->feat_names[bit] ? f->feat_names[bit] : "", bit);

What about leaving the (f->feat_names[bit] ? ... : ...) part
in report_unavailable_features() and just make this function
return "CPUID[...]" or "MSR[...]"?


> +        break;
> +    }
> +    return ret > 0;
> +}
> +
>  static void report_unavailable_features(FeatureWord w, uint32_t mask)
>  {
>      FeatureWordInfo *f = &feature_word_info[w];
>      int i;
> +    char feat_word_dscrp_str[FEATURE_WORD_DESCPTION_LEN];
>  
>      for (i = 0; i < 32; ++i) {
>          if ((1UL << i) & mask) {
> -            const char *reg = get_register_name_32(f->cpuid_reg);
> -            assert(reg);
> -            warn_report("%s doesn't support requested feature: "
> -                        "CPUID.%02XH:%s%s%s [bit %d]",
> +            feature_word_description(feat_word_dscrp_str, f, i);
> +            warn_report("%s doesn't support requested feature: %s",
>                          accel_uses_host_cpuid() ? "host" : "TCG",
> -                        f->cpuid_eax, reg,
> -                        f->feat_names[i] ? "." : "",
> -                        f->feat_names[i] ? f->feat_names[i] : "", i);
> +                        feat_word_dscrp_str);
>          }
>      }
>  }
> @@ -3276,17 +3306,17 @@ static void x86_cpu_get_feature_words(Object *obj, Visitor *v,
>  {
>      uint32_t *array = (uint32_t *)opaque;
>      FeatureWord w;
> -    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS] = { };
> -    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS] = { };
> +    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS_NUM_CPUID] = { };
> +    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS_NUM_CPUID] = { };
>      X86CPUFeatureWordInfoList *list = NULL;
>  
> -    for (w = 0; w < FEATURE_WORDS; w++) {
> +    for (w = 0; w < FEATURE_WORDS_NUM_CPUID; w++) {
>          FeatureWordInfo *wi = &feature_word_info[w];
>          X86CPUFeatureWordInfo *qwi = &word_infos[w];
> -        qwi->cpuid_input_eax = wi->cpuid_eax;
> -        qwi->has_cpuid_input_ecx = wi->cpuid_needs_ecx;
> -        qwi->cpuid_input_ecx = wi->cpuid_ecx;
> -        qwi->cpuid_register = x86_reg_info_32[wi->cpuid_reg].qapi_enum;
> +        qwi->cpuid_input_eax = wi->cpuid.eax;
> +        qwi->has_cpuid_input_ecx = wi->cpuid.needs_ecx;
> +        qwi->cpuid_input_ecx = wi->cpuid.ecx;
> +        qwi->cpuid_register = x86_reg_info_32[wi->cpuid.reg].qapi_enum;

Looks OK, but I would add an
assert(wi->type == CPUID_FEATURE_WORD) on every block of code
that uses the wi->cpuid field.

I would also get rid of FEATURE_WORDS_NUM_CPUID and
FEATURE_WORDS_FIRST_MSR to reduce the chance of future mistakes.
We can use FEATURE_WORDS in this loop and just check wi->type on
each iteration.

>          qwi->features = array[w];
>  
>          /* List will be in reverse order, but order shouldn't matter */
> @@ -3659,12 +3689,20 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
>                                                     bool migratable_only)
>  {
>      FeatureWordInfo *wi = &feature_word_info[w];
> -    uint32_t r;
> +    uint32_t r = 0;
>  
>      if (kvm_enabled()) {
> -        r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
> -                                                    wi->cpuid_ecx,
> -                                                    wi->cpuid_reg);
> +        switch (wi->type) {
> +        case CPUID_FEATURE_WORD:
> +            r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid.eax,
> +                                                wi->cpuid.ecx,
> +                                                wi->cpuid.reg);
> +            break;
> +        case MSR_FEATURE_WORD:
> +            r = kvm_arch_get_supported_msr_feature(kvm_state,
> +                        wi->msr.index);
> +            break;

I'm not sure this is correct in the case of
IA32_ARCH_CAPABILITIES.RSBA: we do want to be able to set RSBA
even if the host doesn't have it set.

Probably you need to handle IA32_ARCH_CAPABILITIES.RSBA as a
special case inside kvm_arch_get_supported_msr_feature().

(And we do want to warn the user in some way if RSBA is set in
the host but not in the guest.  But that's a separate problem.)

> +        }
>      } else if (hvf_enabled()) {
>          r = hvf_get_supported_cpuid(wi->cpuid_eax,
>                                      wi->cpuid_ecx,
> @@ -4732,9 +4770,10 @@ static void x86_cpu_adjust_feat_level(X86CPU *cpu, FeatureWord w)
>  {
>      CPUX86State *env = &cpu->env;
>      FeatureWordInfo *fi = &feature_word_info[w];
> -    uint32_t eax = fi->cpuid_eax;
> +    uint32_t eax = fi->cpuid.eax;
>      uint32_t region = eax & 0xF0000000;
>  
> +    assert(feature_word_info[w].type == CPUID_FEATURE_WORD);
>      if (!env->features[w]) {
>          return;
>      }
> -- 
> 1.8.3.1
> 
>
Paolo Bonzini Aug. 17, 2018, 3:52 p.m. | #4
On 10/08/2018 16:06, Robert Hoo wrote:
> x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.

This should also grow support for MSR feature words.

My suggestion is that you add another patch after patch 1 that expands
the definition of X86CPUFeatureWordInfo like this, and adjusts
x86_cpu_get_feature_words() to match the new C structs.  Then this
patch can add MSR feature support somewhat easily.

The QAPI definitions would then look like this:

diff --git a/qapi/misc.json b/qapi/misc.json
index d450cfef21..eae9243976 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -2663,9 +2663,9 @@
   'data': [ 'EAX', 'EBX', 'ECX', 'EDX', 'ESP', 'EBP', 'ESI', 'EDI' ] }
 
 ##
-# @X86CPUFeatureWordInfo:
+# @X86CPUIDFeatureWordInfo:
 #
-# Information about a X86 CPU feature word
+# Information about an X86 CPUID feature word
 #
 # @cpuid-input-eax: Input EAX value for CPUID instruction for that feature word
 #
@@ -2678,12 +2690,45 @@
 #
 # Since: 1.5
 ##
-{ 'struct': 'X86CPUFeatureWordInfo',
+{ 'struct': 'X86CPUIDFeatureWordInfo',
   'data': { 'cpuid-input-eax': 'int',
             '*cpuid-input-ecx': 'int',
             'cpuid-register': 'X86CPURegister32',
             'features': 'int' } }
 
+##
+# @X86MSRFeatureWordInfo:
+#
+# Information about an X86 MSR feature word
+#
+# @index: Index of the model specific register
+#
+# @cpuid-feature: CPUID feature name that communicates the existance of the MSR
+#
+# @features: value of output register, containing the feature bits
+#
+# Since: 3.1
+##
+{ 'struct': 'X86MSRFeatureWordInfo',
+  'data': { 'index': 'int',
+            'cpuid-feature': 'str',
+            'features': 'int' } }
+
+##
+# @X86CPUFeatureWordInfo:
+#
+# A discriminated record of X86 CPU feature words
+#
+# Since: 3.1
+##
+
+{ 'union': 'X86CPUFeatureWordInfo',
+  'base': { 'type': 'X86CPUFeatureWordType' },
+  'discriminator': 'type',
+  'data': {
+    'cpuid': 'X86CPUIDFeatureWordInfo',
+    'msr': 'X86MSRFeatureWordInfo' }}
+
 ##
 # @DummyForceArrays:
 #

I'm not sure if the cpuid-feature field is useful for libvirt and
other management applications.  Eduardo, what do you think?

Thanks,

Paolo
Robert Hoo Aug. 18, 2018, 9:01 a.m. | #5
On Fri, 2018-08-17 at 10:28 -0300, Eduardo Habkost wrote:
> On Fri, Aug 10, 2018 at 10:06:29PM +0800, Robert Hoo wrote:
> > Add an util function feature_word_description(), which help construct the string
> > describing the feature word (both CPUID and MSR types).
> > 
> > report_unavailable_features(): add MSR_FEATURE_WORD type support.
> > x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
> > x86_cpu_get_supported_feature_word(): add MSR_FEATURE_WORD type support.
> > x86_cpu_adjust_feat_level(): assert the requested feature must be
> > CPUID_FEATURE_WORD type.
> > 
> > Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> > ---
> >  target/i386/cpu.c | 77 +++++++++++++++++++++++++++++++++++++++++--------------
> >  1 file changed, 58 insertions(+), 19 deletions(-)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index f7c70d9..21ed599 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -3024,21 +3024,51 @@ static const TypeInfo host_x86_cpu_type_info = {
> >  
> >  #endif
> >  
> > +/*
> > +*caller should have input str no less than 64 byte length.
> > +*/
> > +#define FEATURE_WORD_DESCPTION_LEN 64
> > +static int feature_word_description(char str[], FeatureWordInfo *f,
> > +                                            uint32_t bit)
> 
> I agree with Eric: g_strup_printf() would be much simpler here.
> 
1 question: I think caller should g_free() the returned str after it
warn_report(), right?
> > +{
> > +    int ret;
> > +
> > +    assert(f->type == CPUID_FEATURE_WORD ||
> > +        f->type == MSR_FEATURE_WORD);
> > +    switch (f->type) {
> > +    case CPUID_FEATURE_WORD:
> > +        {
> > +            const char *reg = get_register_name_32(f->cpuid.reg);
> > +            assert(reg);
> > +            ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> > +                "CPUID.%02XH:%s%s%s [bit %d]",
> > +                f->cpuid.eax, reg,
> > +                f->feat_names[bit] ? "." : "",
> > +                f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> > +            break;
> > +        }
> > +    case MSR_FEATURE_WORD:
> > +        ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> > +            "MSR(%xH).%s [bit %d]",
> > +            f->msr.index,
> > +            f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> 
> What about leaving the (f->feat_names[bit] ? ... : ...) part
> in report_unavailable_features() and just make this function
> return "CPUID[...]" or "MSR[...]"?
> 
> 
> > +        break;
> > +    }
> > +    return ret > 0;
> > +}
> > +
> >  static void report_unavailable_features(FeatureWord w, uint32_t mask)
> >  {
> >      FeatureWordInfo *f = &feature_word_info[w];
> >      int i;
> > +    char feat_word_dscrp_str[FEATURE_WORD_DESCPTION_LEN];
> >  
> >      for (i = 0; i < 32; ++i) {
> >          if ((1UL << i) & mask) {
> > -            const char *reg = get_register_name_32(f->cpuid_reg);
> > -            assert(reg);
> > -            warn_report("%s doesn't support requested feature: "
> > -                        "CPUID.%02XH:%s%s%s [bit %d]",
> > +            feature_word_description(feat_word_dscrp_str, f, i);
> > +            warn_report("%s doesn't support requested feature: %s",
> >                          accel_uses_host_cpuid() ? "host" : "TCG",
> > -                        f->cpuid_eax, reg,
> > -                        f->feat_names[i] ? "." : "",
> > -                        f->feat_names[i] ? f->feat_names[i] : "", i);
> > +                        feat_word_dscrp_str);
> >          }
> >      }
> >  }
> > @@ -3276,17 +3306,17 @@ static void x86_cpu_get_feature_words(Object *obj, Visitor *v,
> >  {
> >      uint32_t *array = (uint32_t *)opaque;
> >      FeatureWord w;
> > -    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS] = { };
> > -    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS] = { };
> > +    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS_NUM_CPUID] = { };
> > +    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS_NUM_CPUID] = { };
> >      X86CPUFeatureWordInfoList *list = NULL;
> >  
> > -    for (w = 0; w < FEATURE_WORDS; w++) {
> > +    for (w = 0; w < FEATURE_WORDS_NUM_CPUID; w++) {
> >          FeatureWordInfo *wi = &feature_word_info[w];
> >          X86CPUFeatureWordInfo *qwi = &word_infos[w];
> > -        qwi->cpuid_input_eax = wi->cpuid_eax;
> > -        qwi->has_cpuid_input_ecx = wi->cpuid_needs_ecx;
> > -        qwi->cpuid_input_ecx = wi->cpuid_ecx;
> > -        qwi->cpuid_register = x86_reg_info_32[wi->cpuid_reg].qapi_enum;
> > +        qwi->cpuid_input_eax = wi->cpuid.eax;
> > +        qwi->has_cpuid_input_ecx = wi->cpuid.needs_ecx;
> > +        qwi->cpuid_input_ecx = wi->cpuid.ecx;
> > +        qwi->cpuid_register = x86_reg_info_32[wi->cpuid.reg].qapi_enum;
> 
> Looks OK, but I would add an
> assert(wi->type == CPUID_FEATURE_WORD) on every block of code
> that uses the wi->cpuid field.
> 
> I would also get rid of FEATURE_WORDS_NUM_CPUID and
> FEATURE_WORDS_FIRST_MSR to reduce the chance of future mistakes.
> We can use FEATURE_WORDS in this loop and just check wi->type on
> each iteration.
> 
> >          qwi->features = array[w];
> >  
> >          /* List will be in reverse order, but order shouldn't matter */
> > @@ -3659,12 +3689,20 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
> >                                                     bool migratable_only)
> >  {
> >      FeatureWordInfo *wi = &feature_word_info[w];
> > -    uint32_t r;
> > +    uint32_t r = 0;
> >  
> >      if (kvm_enabled()) {
> > -        r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
> > -                                                    wi->cpuid_ecx,
> > -                                                    wi->cpuid_reg);
> > +        switch (wi->type) {
> > +        case CPUID_FEATURE_WORD:
> > +            r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid.eax,
> > +                                                wi->cpuid.ecx,
> > +                                                wi->cpuid.reg);
> > +            break;
> > +        case MSR_FEATURE_WORD:
> > +            r = kvm_arch_get_supported_msr_feature(kvm_state,
> > +                        wi->msr.index);
> > +            break;
> 
> I'm not sure this is correct in the case of
> IA32_ARCH_CAPABILITIES.RSBA: we do want to be able to set RSBA
> even if the host doesn't have it set.
> 
> Probably you need to handle IA32_ARCH_CAPABILITIES.RSBA as a
> special case inside kvm_arch_get_supported_msr_feature().
> 
> (And we do want to warn the user in some way if RSBA is set in
> the host but not in the guest.  But that's a separate problem.)

The first part is easy to do. the latter, "to warn the user in some way
if RSBA is set in the host but not in the guest", in
kvm_arch_get_supported_msr_feature(), how can I know if guest has
enabled IA32_ARCH_CAPABILITIES.RSBA or not? or you mean check in some
other place, where is it?
> 
> > +        }
> >      } else if (hvf_enabled()) {
> >          r = hvf_get_supported_cpuid(wi->cpuid_eax,
> >                                      wi->cpuid_ecx,
> > @@ -4732,9 +4770,10 @@ static void x86_cpu_adjust_feat_level(X86CPU *cpu, FeatureWord w)
> >  {
> >      CPUX86State *env = &cpu->env;
> >      FeatureWordInfo *fi = &feature_word_info[w];
> > -    uint32_t eax = fi->cpuid_eax;
> > +    uint32_t eax = fi->cpuid.eax;
> >      uint32_t region = eax & 0xF0000000;
> >  
> > +    assert(feature_word_info[w].type == CPUID_FEATURE_WORD);
> >      if (!env->features[w]) {
> >          return;
> >      }
> > -- 
> > 1.8.3.1
> > 
> > 
>
Robert Hoo Aug. 18, 2018, 12:53 p.m. | #6
On Fri, 2018-08-17 at 17:52 +0200, Paolo Bonzini wrote:
> On 10/08/2018 16:06, Robert Hoo wrote:
> > x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
> 
> This should also grow support for MSR feature words.
> 
> My suggestion is that you add another patch after patch 1 that expands
> the definition of X86CPUFeatureWordInfo like this, and adjusts
> x86_cpu_get_feature_words() to match the new C structs.  Then this
> patch can add MSR feature support somewhat easily.
> 
> The QAPI definitions would then look like this:

I'm not familiar with json language. Can someone else compose this part?
> 
> diff --git a/qapi/misc.json b/qapi/misc.json
> index d450cfef21..eae9243976 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -2663,9 +2663,9 @@
>    'data': [ 'EAX', 'EBX', 'ECX', 'EDX', 'ESP', 'EBP', 'ESI', 'EDI' ] }
>  
>  ##
> -# @X86CPUFeatureWordInfo:
> +# @X86CPUIDFeatureWordInfo:
>  #
> -# Information about a X86 CPU feature word
> +# Information about an X86 CPUID feature word
>  #
>  # @cpuid-input-eax: Input EAX value for CPUID instruction for that feature word
>  #
> @@ -2678,12 +2690,45 @@
>  #
>  # Since: 1.5
>  ##
> -{ 'struct': 'X86CPUFeatureWordInfo',
> +{ 'struct': 'X86CPUIDFeatureWordInfo',
>    'data': { 'cpuid-input-eax': 'int',
>              '*cpuid-input-ecx': 'int',
>              'cpuid-register': 'X86CPURegister32',
>              'features': 'int' } }
>  
> +##
> +# @X86MSRFeatureWordInfo:
> +#
> +# Information about an X86 MSR feature word
> +#
> +# @index: Index of the model specific register
> +#
> +# @cpuid-feature: CPUID feature name that communicates the existance of the MSR
> +#
> +# @features: value of output register, containing the feature bits
> +#
> +# Since: 3.1
> +##
> +{ 'struct': 'X86MSRFeatureWordInfo',
> +  'data': { 'index': 'int',
> +            'cpuid-feature': 'str',
> +            'features': 'int' } }
> +
> +##
> +# @X86CPUFeatureWordInfo:
> +#
> +# A discriminated record of X86 CPU feature words
> +#
> +# Since: 3.1
> +##
> +
> +{ 'union': 'X86CPUFeatureWordInfo',
> +  'base': { 'type': 'X86CPUFeatureWordType' },
> +  'discriminator': 'type',
> +  'data': {
> +    'cpuid': 'X86CPUIDFeatureWordInfo',
> +    'msr': 'X86MSRFeatureWordInfo' }}
> +
>  ##
>  # @DummyForceArrays:
>  #
> 
> I'm not sure if the cpuid-feature field is useful for libvirt and
> other management applications.  Eduardo, what do you think?
> 
> Thanks,
> 
> Paolo
Eduardo Habkost Aug. 18, 2018, 3:10 p.m. | #7
On Sat, Aug 18, 2018 at 05:01:45PM +0800, Robert Hoo wrote:
> On Fri, 2018-08-17 at 10:28 -0300, Eduardo Habkost wrote:
> > On Fri, Aug 10, 2018 at 10:06:29PM +0800, Robert Hoo wrote:
> > > Add an util function feature_word_description(), which help construct the string
> > > describing the feature word (both CPUID and MSR types).
> > > 
> > > report_unavailable_features(): add MSR_FEATURE_WORD type support.
> > > x86_cpu_get_feature_words(): limit to CPUID_FEATURE_WORD only.
> > > x86_cpu_get_supported_feature_word(): add MSR_FEATURE_WORD type support.
> > > x86_cpu_adjust_feat_level(): assert the requested feature must be
> > > CPUID_FEATURE_WORD type.
> > > 
> > > Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> > > ---
> > >  target/i386/cpu.c | 77 +++++++++++++++++++++++++++++++++++++++++--------------
> > >  1 file changed, 58 insertions(+), 19 deletions(-)
> > > 
> > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > > index f7c70d9..21ed599 100644
> > > --- a/target/i386/cpu.c
> > > +++ b/target/i386/cpu.c
> > > @@ -3024,21 +3024,51 @@ static const TypeInfo host_x86_cpu_type_info = {
> > >  
> > >  #endif
> > >  
> > > +/*
> > > +*caller should have input str no less than 64 byte length.
> > > +*/
> > > +#define FEATURE_WORD_DESCPTION_LEN 64
> > > +static int feature_word_description(char str[], FeatureWordInfo *f,
> > > +                                            uint32_t bit)
> > 
> > I agree with Eric: g_strup_printf() would be much simpler here.
> > 
> 1 question: I think caller should g_free() the returned str after it
> warn_report(), right?
> > > +{
> > > +    int ret;
> > > +
> > > +    assert(f->type == CPUID_FEATURE_WORD ||
> > > +        f->type == MSR_FEATURE_WORD);
> > > +    switch (f->type) {
> > > +    case CPUID_FEATURE_WORD:
> > > +        {
> > > +            const char *reg = get_register_name_32(f->cpuid.reg);
> > > +            assert(reg);
> > > +            ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> > > +                "CPUID.%02XH:%s%s%s [bit %d]",
> > > +                f->cpuid.eax, reg,
> > > +                f->feat_names[bit] ? "." : "",
> > > +                f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> > > +            break;
> > > +        }
> > > +    case MSR_FEATURE_WORD:
> > > +        ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
> > > +            "MSR(%xH).%s [bit %d]",
> > > +            f->msr.index,
> > > +            f->feat_names[bit] ? f->feat_names[bit] : "", bit);
> > 
> > What about leaving the (f->feat_names[bit] ? ... : ...) part
> > in report_unavailable_features() and just make this function
> > return "CPUID[...]" or "MSR[...]"?
> > 
> > 
> > > +        break;
> > > +    }
> > > +    return ret > 0;
> > > +}
> > > +
> > >  static void report_unavailable_features(FeatureWord w, uint32_t mask)
> > >  {
> > >      FeatureWordInfo *f = &feature_word_info[w];
> > >      int i;
> > > +    char feat_word_dscrp_str[FEATURE_WORD_DESCPTION_LEN];
> > >  
> > >      for (i = 0; i < 32; ++i) {
> > >          if ((1UL << i) & mask) {
> > > -            const char *reg = get_register_name_32(f->cpuid_reg);
> > > -            assert(reg);
> > > -            warn_report("%s doesn't support requested feature: "
> > > -                        "CPUID.%02XH:%s%s%s [bit %d]",
> > > +            feature_word_description(feat_word_dscrp_str, f, i);
> > > +            warn_report("%s doesn't support requested feature: %s",
> > >                          accel_uses_host_cpuid() ? "host" : "TCG",
> > > -                        f->cpuid_eax, reg,
> > > -                        f->feat_names[i] ? "." : "",
> > > -                        f->feat_names[i] ? f->feat_names[i] : "", i);
> > > +                        feat_word_dscrp_str);
> > >          }
> > >      }
> > >  }
> > > @@ -3276,17 +3306,17 @@ static void x86_cpu_get_feature_words(Object *obj, Visitor *v,
> > >  {
> > >      uint32_t *array = (uint32_t *)opaque;
> > >      FeatureWord w;
> > > -    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS] = { };
> > > -    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS] = { };
> > > +    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS_NUM_CPUID] = { };
> > > +    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS_NUM_CPUID] = { };
> > >      X86CPUFeatureWordInfoList *list = NULL;
> > >  
> > > -    for (w = 0; w < FEATURE_WORDS; w++) {
> > > +    for (w = 0; w < FEATURE_WORDS_NUM_CPUID; w++) {
> > >          FeatureWordInfo *wi = &feature_word_info[w];
> > >          X86CPUFeatureWordInfo *qwi = &word_infos[w];
> > > -        qwi->cpuid_input_eax = wi->cpuid_eax;
> > > -        qwi->has_cpuid_input_ecx = wi->cpuid_needs_ecx;
> > > -        qwi->cpuid_input_ecx = wi->cpuid_ecx;
> > > -        qwi->cpuid_register = x86_reg_info_32[wi->cpuid_reg].qapi_enum;
> > > +        qwi->cpuid_input_eax = wi->cpuid.eax;
> > > +        qwi->has_cpuid_input_ecx = wi->cpuid.needs_ecx;
> > > +        qwi->cpuid_input_ecx = wi->cpuid.ecx;
> > > +        qwi->cpuid_register = x86_reg_info_32[wi->cpuid.reg].qapi_enum;
> > 
> > Looks OK, but I would add an
> > assert(wi->type == CPUID_FEATURE_WORD) on every block of code
> > that uses the wi->cpuid field.
> > 
> > I would also get rid of FEATURE_WORDS_NUM_CPUID and
> > FEATURE_WORDS_FIRST_MSR to reduce the chance of future mistakes.
> > We can use FEATURE_WORDS in this loop and just check wi->type on
> > each iteration.
> > 
> > >          qwi->features = array[w];
> > >  
> > >          /* List will be in reverse order, but order shouldn't matter */
> > > @@ -3659,12 +3689,20 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
> > >                                                     bool migratable_only)
> > >  {
> > >      FeatureWordInfo *wi = &feature_word_info[w];
> > > -    uint32_t r;
> > > +    uint32_t r = 0;
> > >  
> > >      if (kvm_enabled()) {
> > > -        r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
> > > -                                                    wi->cpuid_ecx,
> > > -                                                    wi->cpuid_reg);
> > > +        switch (wi->type) {
> > > +        case CPUID_FEATURE_WORD:
> > > +            r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid.eax,
> > > +                                                wi->cpuid.ecx,
> > > +                                                wi->cpuid.reg);
> > > +            break;
> > > +        case MSR_FEATURE_WORD:
> > > +            r = kvm_arch_get_supported_msr_feature(kvm_state,
> > > +                        wi->msr.index);
> > > +            break;
> > 
> > I'm not sure this is correct in the case of
> > IA32_ARCH_CAPABILITIES.RSBA: we do want to be able to set RSBA
> > even if the host doesn't have it set.
> > 
> > Probably you need to handle IA32_ARCH_CAPABILITIES.RSBA as a
> > special case inside kvm_arch_get_supported_msr_feature().
> > 
> > (And we do want to warn the user in some way if RSBA is set in
> > the host but not in the guest.  But that's a separate problem.)
> 
> The first part is easy to do. the latter, "to warn the user in some way
> if RSBA is set in the host but not in the guest", in
> kvm_arch_get_supported_msr_feature(), how can I know if guest has
> enabled IA32_ARCH_CAPABILITIES.RSBA or not? or you mean check in some
> other place, where is it?

Probably X86CPU realize function is an obvious place, but the
main problem is that we don't have an appropriate channel to
report that warning except stderr (making the warning useless for
users that are not running QEMU directly).

We also need to ensure QEMU is doing its job before it complains
to the user: before printing a warning about unsafe
configuration, we should try to make QEMU enable safe
configuration by default.

Patch

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index f7c70d9..21ed599 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -3024,21 +3024,51 @@  static const TypeInfo host_x86_cpu_type_info = {
 
 #endif
 
+/*
+*caller should have input str no less than 64 byte length.
+*/
+#define FEATURE_WORD_DESCPTION_LEN 64
+static int feature_word_description(char str[], FeatureWordInfo *f,
+                                            uint32_t bit)
+{
+    int ret;
+
+    assert(f->type == CPUID_FEATURE_WORD ||
+        f->type == MSR_FEATURE_WORD);
+    switch (f->type) {
+    case CPUID_FEATURE_WORD:
+        {
+            const char *reg = get_register_name_32(f->cpuid.reg);
+            assert(reg);
+            ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
+                "CPUID.%02XH:%s%s%s [bit %d]",
+                f->cpuid.eax, reg,
+                f->feat_names[bit] ? "." : "",
+                f->feat_names[bit] ? f->feat_names[bit] : "", bit);
+            break;
+        }
+    case MSR_FEATURE_WORD:
+        ret = snprintf(str, FEATURE_WORD_DESCPTION_LEN,
+            "MSR(%xH).%s [bit %d]",
+            f->msr.index,
+            f->feat_names[bit] ? f->feat_names[bit] : "", bit);
+        break;
+    }
+    return ret > 0;
+}
+
 static void report_unavailable_features(FeatureWord w, uint32_t mask)
 {
     FeatureWordInfo *f = &feature_word_info[w];
     int i;
+    char feat_word_dscrp_str[FEATURE_WORD_DESCPTION_LEN];
 
     for (i = 0; i < 32; ++i) {
         if ((1UL << i) & mask) {
-            const char *reg = get_register_name_32(f->cpuid_reg);
-            assert(reg);
-            warn_report("%s doesn't support requested feature: "
-                        "CPUID.%02XH:%s%s%s [bit %d]",
+            feature_word_description(feat_word_dscrp_str, f, i);
+            warn_report("%s doesn't support requested feature: %s",
                         accel_uses_host_cpuid() ? "host" : "TCG",
-                        f->cpuid_eax, reg,
-                        f->feat_names[i] ? "." : "",
-                        f->feat_names[i] ? f->feat_names[i] : "", i);
+                        feat_word_dscrp_str);
         }
     }
 }
@@ -3276,17 +3306,17 @@  static void x86_cpu_get_feature_words(Object *obj, Visitor *v,
 {
     uint32_t *array = (uint32_t *)opaque;
     FeatureWord w;
-    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS] = { };
-    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS] = { };
+    X86CPUFeatureWordInfo word_infos[FEATURE_WORDS_NUM_CPUID] = { };
+    X86CPUFeatureWordInfoList list_entries[FEATURE_WORDS_NUM_CPUID] = { };
     X86CPUFeatureWordInfoList *list = NULL;
 
-    for (w = 0; w < FEATURE_WORDS; w++) {
+    for (w = 0; w < FEATURE_WORDS_NUM_CPUID; w++) {
         FeatureWordInfo *wi = &feature_word_info[w];
         X86CPUFeatureWordInfo *qwi = &word_infos[w];
-        qwi->cpuid_input_eax = wi->cpuid_eax;
-        qwi->has_cpuid_input_ecx = wi->cpuid_needs_ecx;
-        qwi->cpuid_input_ecx = wi->cpuid_ecx;
-        qwi->cpuid_register = x86_reg_info_32[wi->cpuid_reg].qapi_enum;
+        qwi->cpuid_input_eax = wi->cpuid.eax;
+        qwi->has_cpuid_input_ecx = wi->cpuid.needs_ecx;
+        qwi->cpuid_input_ecx = wi->cpuid.ecx;
+        qwi->cpuid_register = x86_reg_info_32[wi->cpuid.reg].qapi_enum;
         qwi->features = array[w];
 
         /* List will be in reverse order, but order shouldn't matter */
@@ -3659,12 +3689,20 @@  static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
                                                    bool migratable_only)
 {
     FeatureWordInfo *wi = &feature_word_info[w];
-    uint32_t r;
+    uint32_t r = 0;
 
     if (kvm_enabled()) {
-        r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
-                                                    wi->cpuid_ecx,
-                                                    wi->cpuid_reg);
+        switch (wi->type) {
+        case CPUID_FEATURE_WORD:
+            r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid.eax,
+                                                wi->cpuid.ecx,
+                                                wi->cpuid.reg);
+            break;
+        case MSR_FEATURE_WORD:
+            r = kvm_arch_get_supported_msr_feature(kvm_state,
+                        wi->msr.index);
+            break;
+        }
     } else if (hvf_enabled()) {
         r = hvf_get_supported_cpuid(wi->cpuid_eax,
                                     wi->cpuid_ecx,
@@ -4732,9 +4770,10 @@  static void x86_cpu_adjust_feat_level(X86CPU *cpu, FeatureWord w)
 {
     CPUX86State *env = &cpu->env;
     FeatureWordInfo *fi = &feature_word_info[w];
-    uint32_t eax = fi->cpuid_eax;
+    uint32_t eax = fi->cpuid.eax;
     uint32_t region = eax & 0xF0000000;
 
+    assert(feature_word_info[w].type == CPUID_FEATURE_WORD);
     if (!env->features[w]) {
         return;
     }