i386: Add CPUID bit for CLZERO and XSAVEERPTR

[PATCH] i386: Add CPUID bit for CLZERO and XSAVEERPTR

Posted by Sebastian Andrzej Siewior 4 years, 6 months ago

The CPUID bits CLZERO and XSAVEERPTR are availble on AMD's ZEN platform
and could be passed to the guest.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---

I tweaked the kernel to expose these flags and figured out that this is
also missing in order see those bits in the guest.

 target/i386/cpu.c | 2 +-
 target/i386/cpu.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index fbed2eb804e32..e00ef3c917391 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1113,7 +1113,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
     [FEAT_8000_0008_EBX] = {
         .type = CPUID_FEATURE_WORD,
         .feat_names = {
-            NULL, NULL, NULL, NULL,
+            "clzero", NULL, "xsaveerptr", NULL,
             NULL, NULL, NULL, NULL,
             NULL, "wbnoinvd", NULL, NULL,
             "ibpb", NULL, NULL, NULL,
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 0732e059ec989..cc475c703fc4d 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -689,6 +689,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
 #define CPUID_7_0_EDX_ARCH_CAPABILITIES (1U << 29)  /*Arch Capabilities*/
 #define CPUID_7_0_EDX_SPEC_CTRL_SSBD  (1U << 31) /* Speculative Store Bypass Disable */
 
+#define CPUD_800_008_EBX_CLZERO		(1U << 0) /* CLZERO instruction */
+#define CPUD_800_008_EBX_XSAVEERPTR	(1U << 2) /* Always save/restore FP error pointers */
 #define CPUID_8000_0008_EBX_WBNOINVD  (1U << 9)  /* Write back and
                                                                              do not invalidate cache */
 #define CPUID_8000_0008_EBX_IBPB    (1U << 12) /* Indirect Branch Prediction Barrier */
-- 
2.23.0

Re: [PATCH] i386: Add CPUID bit for CLZERO and XSAVEERPTR

Posted by Paolo Bonzini 4 years, 6 months ago

On 25/09/19 23:49, Sebastian Andrzej Siewior wrote:
> The CPUID bits CLZERO and XSAVEERPTR are availble on AMD's ZEN platform
> and could be passed to the guest.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> 
> I tweaked the kernel to expose these flags and figured out that this is
> also missing in order see those bits in the guest.
> 
>  target/i386/cpu.c | 2 +-
>  target/i386/cpu.h | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index fbed2eb804e32..e00ef3c917391 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -1113,7 +1113,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>      [FEAT_8000_0008_EBX] = {
>          .type = CPUID_FEATURE_WORD,
>          .feat_names = {
> -            NULL, NULL, NULL, NULL,
> +            "clzero", NULL, "xsaveerptr", NULL,
>              NULL, NULL, NULL, NULL,
>              NULL, "wbnoinvd", NULL, NULL,
>              "ibpb", NULL, NULL, NULL,
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 0732e059ec989..cc475c703fc4d 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -689,6 +689,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  #define CPUID_7_0_EDX_ARCH_CAPABILITIES (1U << 29)  /*Arch Capabilities*/
>  #define CPUID_7_0_EDX_SPEC_CTRL_SSBD  (1U << 31) /* Speculative Store Bypass Disable */
>  
> +#define CPUD_800_008_EBX_CLZERO		(1U << 0) /* CLZERO instruction */
> +#define CPUD_800_008_EBX_XSAVEERPTR	(1U << 2) /* Always save/restore FP error pointers */
>  #define CPUID_8000_0008_EBX_WBNOINVD  (1U << 9)  /* Write back and
>                                                                               do not invalidate cache */
>  #define CPUID_8000_0008_EBX_IBPB    (1U << 12) /* Indirect Branch Prediction Barrier */
> 

Yup, queued this one.

Paolo

Re: [PATCH] i386: Add CPUID bit for CLZERO and XSAVEERPTR

Posted by Paolo Bonzini 4 years, 6 months ago

On 25/09/19 23:49, Sebastian Andrzej Siewior wrote:
>  #define CPUID_7_0_EDX_SPEC_CTRL_SSBD  (1U << 31) /* Speculative Store Bypass Disable */
>  
> +#define CPUD_800_008_EBX_CLZERO		(1U << 0) /* CLZERO instruction */
> +#define CPUD_800_008_EBX_XSAVEERPTR	(1U << 2) /* Always save/restore FP error pointers */
>  #define CPUID_8000_0008_EBX_WBNOINVD  (1U << 9)  /* Write back and

Well, there are obvious typos here but I can fix them for you.

Which processors have these?

Paolo

Re: [PATCH] i386: Add CPUID bit for CLZERO and XSAVEERPTR

Posted by Sebastian Andrzej Siewior 4 years, 6 months ago

On 2019-09-26 13:06:34 [+0200], Paolo Bonzini wrote:
> On 25/09/19 23:49, Sebastian Andrzej Siewior wrote:
> >  #define CPUID_7_0_EDX_SPEC_CTRL_SSBD  (1U << 31) /* Speculative Store Bypass Disable */
> >  
> > +#define CPUD_800_008_EBX_CLZERO		(1U << 0) /* CLZERO instruction */
> > +#define CPUD_800_008_EBX_XSAVEERPTR	(1U << 2) /* Always save/restore FP error pointers */
> >  #define CPUID_8000_0008_EBX_WBNOINVD  (1U << 9)  /* Write back and
> 
> Well, there are obvious typos here but I can fix them for you.

Sorry for the missing I.

> Which processors have these?

There are mention in AMD document [0]. I *think* there were introduced
in Zen, see them on a Ryzen and Epyc.

[0] https://www.amd.com/system/files/TechDocs/24594.pdf

> Paolo

Sebastian