Re: [Xen-devel] [PATCH v9 10/25] x86: refactor psr: L3 CAT: set value: assemble features value array.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.03.17 at 10:05, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> On 17-03-28 11:12:43, Yi Sun wrote:
>> On 17-03-27 04:17:28, Jan Beulich wrote:
>> > >>> On 16.03.17 at 12:08, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
>> > > --- a/xen/arch/x86/psr.c
>> > > +++ b/xen/arch/x86/psr.c
> [...]
> 
>> > >  static int gather_val_array(uint32_t val[],
>> > > @@ -589,7 +672,34 @@ static int gather_val_array(uint32_t val[],
>> > >                              const struct psr_socket_info *info,
>> > >                              unsigned int old_cos)
>> > >  {
>> > > -    return -EINVAL;
>> > > +    const struct feat_node *feat;
>> > > +    unsigned int i;
>> > > +
>> > > +    if ( !val )
>> > > +        return -EINVAL;
>> > > +
>> > > +    /* Get all features current values according to old_cos. */
>> > > +    for ( i = 0; i < PSR_SOCKET_MAX_FEAT; i++ )
>> > > +    {
>> > > +        if ( !info->features[i] )
>> > > +            continue;
>> > > +
>> > > +        feat = info->features[i];
>> > > +
>> > > +        if ( old_cos > feat->ops.get_cos_max(feat) )
>> > > +            old_cos = 0;
>> > > +
>> > > +        /* value getting order is same as feature array */
>> > > +        feat->ops.get_old_val(val, feat, old_cos);
>> > > +
>> > > +        array_len -= feat->cos_num;
>> > 
>> > So this I should really have asked about on a much earlier patch,
>> > but I've recognize the oddity only now: Why is cos_num
>> > per-feature-node instead of per-feature? This should really be a
>> > field in struct feat_ops (albeit the name "ops" then will be slightly
>> > misleading, but I think that's tolerable if you can't think of a better
>> > name).
>> > 
>> Ok, I got your meaning. How about 'feat_props'? No matter operations or
>> variables are all properties of the feature.
>> 
> One more thing here. If we move 'cos_max' into 'feat_ops', we cannot declare
> 'feat_ops' as const. Because we have to assign value to 'cos_max' in
> cat_init_feature().

I don't see a problem with this. It's only the static variable which
can't be const then anymore. The pointer used everywhere else
easily can be, afaict.

Jan


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