Re: [Xen-devel] [PATCH v3 03/13] xen: introduce cpumask_from_bitmap

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-04-25 at 10:24 +0100, Jan Beulich wrote:
> >>> On 24.04.13 at 21:07, Stefano Stabellini 
> >>> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > +static inline cpumask_t cpumask_from_bitmap(unsigned long *bits, int 
> > nr_bits)
> > +{
> > +    cpumask_t mask;
> > +    int len = nr_bits < nr_cpumask_bits ? nr_bits : nr_cpumask_bits;
> 
> min(nr_bits, nr_cpumask_bits)
> 
> > +
> > +    memset(&mask, 0x00, sizeof(mask));
> 
> bitmap_zero().
> 
> > +   bitmap_copy(mask.bits, bits, len);
> 
> Hard tab.
> 
> > +
> > +    return mask;
> > +}
> 
> And most importantly: Why? This isn't an operation that should
> commonly be done, and hence having a utility function for this
> seems to invite for abuse rather than really help.

I suggested it, we are emulating an instruction which provides a bitmap
of the CPUs to operate on. It seemed nicer to me to have a helper rather
than to open-code accesses under the hood of the cpumask interface.

Ian.



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