Re: [Xen-devel] [Patch 2/6] Xen/MCE: remove mcg_ctl and other adjustment for future vMCE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.07.12 at 11:39, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> @@ -175,11 +179,16 @@
>                     *val);
>          break;
>      case MSR_IA32_MCG_CTL:
> -        /* Always 0 if no CTL support */
>          if ( cur->arch.mcg_cap & MCG_CTL_P )
> -            *val = vmce->mcg_ctl & h_mcg_ctl;
> -        mce_printk(MCE_VERBOSE, "MCE: rdmsr MCG_CTL 0x%"PRIx64"\n",
> -                   *val);
> +        {
> +            *val = ~0UL;
> +            mce_printk(MCE_VERBOSE, "MCE: rdmsr MCG_CTL 0x%"PRIx64"\n", 
> *val);
> +        }
> +        else
> +        {
> +            mce_printk(MCE_QUIET, "MCE: no MCG_CTL\n");
> +            ret = -1;

Is there a particular reason to make this access fault here, when
it didn't before? I.e. was there anything wrong with the previous
approach of returning zero on reads and ignoring writes when
!MCG_CTL_P?

> +        }
>          break;
>      default:
>          ret = mce_bank_msr(cur, msr) ? bank_mce_rdmsr(cur, msr, val) : 0;
> @@ -287,15 +296,16 @@
>      struct domain_mca_msrs *vmce = dom_vmce(cur->domain);
>      int ret = 1;
>  
> -    if ( !g_mcg_cap )
> -        return 0;
> -
>      spin_lock(&vmce->lock);
>  
>      switch ( msr )
>      {
>      case MSR_IA32_MCG_CTL:
> -        vmce->mcg_ctl = val;
> +        if ( !(cur->arch.mcg_cap & MCG_CTL_P) )
> +        {
> +            mce_printk(MCE_QUIET, "MCE: no MCG_CTL\n");
> +            ret = -1;
> +        }
>          break;
>      case MSR_IA32_MCG_STATUS:
>          vmce->mcg_status = val;

Other than that, the patch looks fine to me.

Jan


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