Re: [Xen-devel] [PATCH 2 of 2] vpmu: Add the BTS extension

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.02.12 at 14:01, Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx> wrote:
> @@ -401,7 +401,31 @@ static int core2_vpmu_do_wrmsr(unsigned 
>      struct core2_vpmu_context *core2_vpmu_cxt = NULL;
>  
>      if ( !core2_vpmu_msr_common_check(msr, &type, &index) )
> +    {
> +        /* Special handling for BTS */
> +        if ( msr == MSR_IA32_DEBUGCTLMSR )
> +        {
> +            uint64_t supported = IA32_DEBUGCTLMSR_TR | IA32_DEBUGCTLMSR_BTS |
> +                                 IA32_DEBUGCTLMSR_BTINT;

Was the code to make BTINT work magically in place already? I can't
spot anything to the effect in the patch...

> +
> +            if ( cpu_has(&current_cpu_data, X86_FEATURE_DSCPL) )
> +            {
> +                supported |= IA32_DEBUGCTLMSR_BTS_OFF_OS |
> +                                 IA32_DEBUGCTLMSR_BTS_OFF_USR;
> +            }
> +            if ( msr_content & supported  )
> +            {
> +                if ( !vpmu_is_set(vpmu, VPMU_CPU_HAS_BTS) )
> +                {
> +                    gdprintk(XENLOG_WARNING, "Debug Store is not supported 
> on this cpu\n");
> +                    vmx_inject_hw_exception(TRAP_gp_fault, 0);
> +                    return 0;
> +                }
> +                return 1;
> +            }
> +        }
>          return 0;
> +    }
>  
>      core2_vpmu_cxt = vpmu->context;
>      switch ( msr )
> @@ -420,8 +444,26 @@ static int core2_vpmu_do_wrmsr(unsigned 
>                       "which is not supported.\n");
>          return 1;
>      case MSR_IA32_DS_AREA:
> -        gdprintk(XENLOG_WARNING, "Guest setting of DTS is ignored.\n");
> -        return 1;
> +        if ( vpmu_is_set(vpmu, VPMU_CPU_HAS_DS) )
> +        {
> +            if (!msr_content || !is_canonical_address(msr_content))
> +            {
> +                gdprintk(XENLOG_WARNING, "Illegal address for IA32_DS_AREA: 
> 0x%lx\n",
> +                                                            msr_content);
> +                vmx_inject_hw_exception(TRAP_gp_fault, 0);
> +                return 1;
> +            }
> +            else
> +            {
> +                core2_vpmu_cxt->pmu_enable->ds_area_enable = msr_content ? 1 
> : 0;
> +                break;

How do you manage to get away without storing the value the guest
attempted to write?

Jan

> +            }
> +        }
> +        else
> +        {
> +            gdprintk(XENLOG_WARNING, "Guest setting of DTS is ignored.\n");
> +            return 1;
> +        }
>      case MSR_CORE_PERF_GLOBAL_CTRL:
>          global_ctrl = msr_content;
>          for ( i = 0; i < core2_get_pmc_count(); i++ )



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