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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 25 Apr 2013, Jan Beulich wrote:
> >>> On 25.04.13 at 12:35, Stefano Stabellini 
> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> wrote:
> > On Thu, 25 Apr 2013, Jan Beulich wrote:
> >> >>> On 25.04.13 at 12:01, Stefano Stabellini 
> >> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> >> wrote:
> >> > On Thu, 25 Apr 2013, 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.
> >> > 
> >> > TBH I have done it to address Ian's comment, I don't have a strong
> >> > opinion on this.
> >> > However it is true that from an API point of view, cpumask_from_bitmap
> >> > allows us to cover the new use case without breaking the cpumask
> >> > abstraction.
> >> 
> >> Rather than adding a new abstraction that's used for a single
> >> special case, and if open coding is undesirable, I'd prefer if you
> >> used bitmap_to_xenctl_bitmap() plus xenctl_bitmap_to_cpumask()
> >> if at all possible.
> > 
> > Both functions do copy_to/from_guest and use xmalloc, I don't think I
> > can use them.
> 
> Hmm, ugly. But okay then...

Is that an ack? ;-)

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