Two Fixes for xsave compoent features

[PATCH 1/2] i386/cpu: Clear FEAT_XSAVE_COMP_{LO, HI} when XSAVE is not available

Posted by Xiaoyao Li 5 years, 6 months ago

Per Intel SDM vol 1, 13.2, if CPUID.1:ECX.XSAVE[bit 26] is 0, the
processor provides no further enumeration through CPUID function 0DH.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 target/i386/cpu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 1e5123251d74..f5f11603e805 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6261,6 +6261,8 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu)
     uint64_t mask;
 
     if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
+        env->features[FEAT_XSAVE_COMP_LO] = 0;
+        env->features[FEAT_XSAVE_COMP_HI] = 0;
         return;
     }
 
-- 
2.18.4

Re: [PATCH 1/2] i386/cpu: Clear FEAT_XSAVE_COMP_{LO,HI} when XSAVE is not available

Posted by Eduardo Habkost 5 years, 6 months ago

On Thu, Jul 16, 2020 at 04:20:18PM +0800, Xiaoyao Li wrote:
> Per Intel SDM vol 1, 13.2, if CPUID.1:ECX.XSAVE[bit 26] is 0, the
> processor provides no further enumeration through CPUID function 0DH.

Can you explain what's the bug you are trying to fix?
env->features[FEAT_XSAVE_COMP_*] is already initialized as zero.

> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  target/i386/cpu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 1e5123251d74..f5f11603e805 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6261,6 +6261,8 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu)
>      uint64_t mask;
>  
>      if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
> +        env->features[FEAT_XSAVE_COMP_LO] = 0;
> +        env->features[FEAT_XSAVE_COMP_HI] = 0;
>          return;
>      }
>  
> -- 
> 2.18.4
> 

-- 
Eduardo

Re: [PATCH 1/2] i386/cpu: Clear FEAT_XSAVE_COMP_{LO, HI} when XSAVE is not available

Posted by Xiaoyao Li 5 years, 6 months ago

On 7/16/2020 11:15 PM, Eduardo Habkost wrote:
> On Thu, Jul 16, 2020 at 04:20:18PM +0800, Xiaoyao Li wrote:
>> Per Intel SDM vol 1, 13.2, if CPUID.1:ECX.XSAVE[bit 26] is 0, the
>> processor provides no further enumeration through CPUID function 0DH.
> 
> Can you explain what's the bug you are trying to fix?
> env->features[FEAT_XSAVE_COMP_*] is already initialized as zero.

When "-cpu host", it's not zero I think.

> 
>>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> ---
>>   target/i386/cpu.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index 1e5123251d74..f5f11603e805 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -6261,6 +6261,8 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu)
>>       uint64_t mask;
>>   
>>       if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
>> +        env->features[FEAT_XSAVE_COMP_LO] = 0;
>> +        env->features[FEAT_XSAVE_COMP_HI] = 0;
>>           return;
>>       }
>>   
>> -- 
>> 2.18.4
>>
>

Re: [PATCH 1/2] i386/cpu: Clear FEAT_XSAVE_COMP_{LO, HI} when XSAVE is not available

Posted by Paolo Bonzini 5 years, 5 months ago

On 16/07/20 10:20, Xiaoyao Li wrote:
> Per Intel SDM vol 1, 13.2, if CPUID.1:ECX.XSAVE[bit 26] is 0, the
> processor provides no further enumeration through CPUID function 0DH.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  target/i386/cpu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 1e5123251d74..f5f11603e805 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6261,6 +6261,8 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu)
>      uint64_t mask;
>  
>      if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
> +        env->features[FEAT_XSAVE_COMP_LO] = 0;
> +        env->features[FEAT_XSAVE_COMP_HI] = 0;
>          return;
>      }
>  
> 

Queued this patch, noting in the commit message that it affects "-cpu
host,-xsave".

Paolo