Re: [Xen-devel] [PATCH v10 08/25] x86: refactor psr: L3 CAT: implement get value flow.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.04.17 at 13:13, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> On 17-04-06 02:40:01, Jan Beulich wrote:
>> >>> On 06.04.17 at 08:10, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
>> > On 17-04-05 09:51:44, Jan Beulich wrote:
>> >> >>> On 01.04.17 at 15:53, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> 
> [...]
>> >> > --- a/xen/arch/x86/psr.c
>> >> > +++ b/xen/arch/x86/psr.c
>> >> > @@ -97,6 +97,10 @@ struct feat_node {
>> >> >          /* get_feat_info is used to get feature HW info. */
>> >> >          bool (*get_feat_info)(const struct feat_node *feat,
>> >> >                                uint32_t data[], unsigned int array_len);
>> >> > +
>> >> > +        /* get_val is used to get feature COS register value. */
>> >> > +        void (*get_val)(const struct feat_node *feat, unsigned int cos,
>> >> > +                        uint32_t *val);
>> >> >      } *props;
>> >> >  
>> >> >      uint32_t cos_reg_val[MAX_COS_REG_CNT];
>> >> > @@ -265,10 +269,17 @@ static bool cat_get_feat_info(const struct 
>> >> > feat_node 
> *feat,
>> >> >      return true;
>> >> >  }
>> >> >  
>> >> > +static void cat_get_val(const struct feat_node *feat, unsigned int cos,
>> >> > +                        uint32_t *val)
>> >> > +{
>> >> > +    *val = feat->cos_reg_val[cos];
>> >> > +}
>> >> 
>> >> This can be done by the caller - there's nothing feature specific in
>> >> here, so there's no need for a hook.
>> >> 
>> > Hmm, CDP's 'get_val' is different so that we need this hook. Do you mean I
>> > should create this CAT's 'get_val' hook when implementing CDP patch?
>> 
>> No, not really - doesn't the type-to-index mapping array (or
>> whichever way it ends up being) all take care of the feature
>> specific aspects here?
>>
> For CDP case, the value getting depends on type. If we don't have this hook,
> we have to do special handling in main flow.
> 
> Still use 'fits_cos_max' as example:
>     /* For CDP, DATA is the first item in val[], CODE is the second. */
>     for ( j = 0; j < feat->props->cos_num; j++ )                       
>     {                                                                  
>         feat->props->get_val(feat, 0, feat->props->type[j],            
>                              &default_val);                          
>         if ( val[j] != default_val )                              
>             return false;                                       
>     } 
> 
> We want to get CDP DATA and CODE one by one to compare with val[] as the 
> order.
> If we do not have 'get_val', how can we handle this case? Getting DATA is
> different with getting CODE which is shown below. Even we have 
> type-to-index,
> we still need the hook to help I think. So far, I cannot figure out a 
> generic
> way.
> Get data: (feat)->cos_reg_val[(cos) * 2]
> Get code: (feat)->cos_reg_val[(cos) * 2 + 1]

Which makes it

    for ( i = 0; i < props->cos_num; ++i )
        val[i] = feat->cos_reg_val[cos * props->cos_num + i];

?

Jan


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