Re: [PATCH v3 2/4] target/i386: Remove monitor from some CPU models

[Eduardo Habkost]

On Wed, Feb 12, 2020 at 04:13:26PM +0800, Tao Xu wrote:
> Add new version of Snowridge, Denverton, Opteron_G3, EPYC, and Dhyana
> CPU model to remove MONITOR/MWAIT feature.
> 
> After QEMU/KVM use "-overcommit cpu-pm=on" to expose MONITOR/MWAIT
> (commit id 6f131f13e68d648a8e4f083c667ab1acd88ce4cd), the MONITOR/MWAIT
> feature in these CPU model is unused.
> 
> Signed-off-by: Tao Xu <address@hidden>

What exactly is the problem you are trying to fix?

No CPU model will ever have monitor=on set by default with KVM,
because kvm_default_props has a monitor=off element.

> ---
>  target/i386/cpu.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 848c992cd3..6905e4eabd 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -3731,6 +3731,14 @@ static X86CPUDefinition builtin_x86_defs[] = {
>                      { /* end of list */ },
>                  },
>              },
> +            {
> +                .version = 3,
> +                .props = (PropValue[]) {
> +                    /* mpx was already removed by -v2 above */
> +                    { "monitor", "off" },
> +                    { /* end of list */ },
> +                },
> +            },
>              { /* end of list */ },
>          },
>      },
> @@ -3842,6 +3850,17 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_EXT3_ABM | CPUID_EXT3_SVM | CPUID_EXT3_LAHF_LM,
>          .xlevel = 0x80000008,
>          .model_id = "AMD Opteron 23xx (Gen 3 Class Opteron)",
> +        .versions = (X86CPUVersionDefinition[]) {
> +            { .version = 1 },
> +            {
> +                .version = 2,
> +                .props = (PropValue[]) {
> +                    { "monitor", "off" },
> +                    { /* end of list */ },
> +                },
> +            },
> +            { /* end of list */ },
> +        },
>      },
>      {
>          .name = "Opteron_G4",
> @@ -3966,6 +3985,14 @@ static X86CPUDefinition builtin_x86_defs[] = {
>                      { /* end of list */ }
>                  }
>              },
> +            {
> +                .version = 3,
> +                .props = (PropValue[]) {
> +                    /* ibpb was already enabled by -v2 above */
> +                    { "monitor", "off" },
> +                    { /* end of list */ },
> +                },
> +            },
>              { /* end of list */ }
>          }
>      },
> @@ -4018,6 +4045,17 @@ static X86CPUDefinition builtin_x86_defs[] = {
>          .xlevel = 0x8000001E,
>          .model_id = "Hygon Dhyana Processor",
>          .cache_info = &epyc_cache_info,
> +        .versions = (X86CPUVersionDefinition[]) {
> +            { .version = 1 },
> +            {
> +                .version = 2,
> +                .props = (PropValue[]) {
> +                    { "monitor", "off" },
> +                    { /* end of list */ },
> +                },
> +            },
> +            { /* end of list */ },
> +        },
>      },
>  };
>  
> -- 
> 2.20.1
> 
> 

-- 
Eduardo