Re: [Xen-devel] [PATCH v24 08/15] x86/VPMU: When handling MSR accesses, leave fault injection to callers

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.06.15 at 17:04, <boris.ostrovsky@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/vmx/vpmu_core2.c
> +++ b/xen/arch/x86/hvm/vmx/vpmu_core2.c
> @@ -454,36 +454,41 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, 
> uint64_t msr_content,
>                               IA32_DEBUGCTLMSR_BTS_OFF_USR;
>              if ( !(msr_content & ~supported) &&
>                   vpmu_is_set(vpmu, VPMU_CPU_HAS_BTS) )
> -                return 1;
> +                return 0;
>              if ( (msr_content & supported) &&
>                   !vpmu_is_set(vpmu, VPMU_CPU_HAS_BTS) )
>                  printk(XENLOG_G_WARNING
>                         "%pv: Debug Store unsupported on this CPU\n",
>                         current);
>          }
> -        return 0;
> +        return -EINVAL;
>      }
>  
>      ASSERT(!supported);
>  
> +    if ( type == MSR_TYPE_COUNTER &&
> +         (msr_content &
> +          ~((1ull << core2_get_bitwidth_fix_count()) - 1)) )
> +        /* Writing unsupported bits to a fixed counter */
> +        return -EINVAL;
> +
>      core2_vpmu_cxt = vpmu->context;
>      enabled_cntrs = vpmu->priv_context;
>      switch ( msr )
>      {
>      case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
>          core2_vpmu_cxt->global_status &= ~msr_content;
> -        return 1;
> +        return 0;
>      case MSR_CORE_PERF_GLOBAL_STATUS:
>          gdprintk(XENLOG_INFO, "Can not write readonly MSR: "
>                   "MSR_PERF_GLOBAL_STATUS(0x38E)!\n");
> -        hvm_inject_hw_exception(TRAP_gp_fault, 0);
> -        return 1;
> +        return -EINVAL;

Is it intentional that you convert a success to a failure here? If so,
this should be mentioned (with reason) in the commit message. If
not, this should be adjusted to there's no behavioral change here.

Jan


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