Re: [PATCH 01 of 11 v3] xen, libxc: rename xenctl_cpumap to xenctl_bitmap

[Dario Faggioli <dario.faggioli@citrix.com>]

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On mar, 2013-03-12 at 15:46 +0000, Ian Campbell wrote:
> On Fri, 2013-02-01 at 11:01 +0000, Dario Faggioli wrote:
> > This is in preparation of introducing NUMA node-affinity maps.
> 
> The second patch doesn't use this new infrastrucuture though, and has
> "typedef uint8_t *xc_nodemap_t" instead. 
>
Indeed, exactly as it happens for xc_cpumap_t, independently from both
the first and the second patch of this series. However, the second patch
defines xenctl_bitmap_to_nodemask() and nodemask_to_xenctl_bitmap(),
which is what uses xenctl_bitmap.

Fact is xenctl_bitmap is used within DOMCTLs, while xc_{cpu,node}map_t
is used by xc_*_{set,get}_affinity(), which is what, for instance, libxl
calls.

The split and the ordering of the series is meant at allowing patch 2 to
define everything that is nodemap related, inside libxc, including the
xenctl_bitmap_to_nodemask() (and reverse) functions above. Actual usage
of both the types and related interfaces, only happen in subsequent
patches.

> Which makes sense since a
> node-affinity map is not a bitmap, is it?
> 
They all are the same thing, but represented differently depending on
where we are.

All that being said... Did I answer? :-)

> > diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> > --- a/xen/include/public/xen.h
> > +++ b/xen/include/public/xen.h
> > @@ -851,9 +851,9 @@ typedef uint8_t xen_domain_handle_t[16];
> >  #endif
> > 
> >  #ifndef __ASSEMBLY__
> > -struct xenctl_cpumap {
> > +struct xenctl_bitmap {
> >      XEN_GUEST_HANDLE_64(uint8) bitmap;
> > -    uint32_t nr_cpus;
> > +    uint32_t nr_elems;
> 
> Is this really "nr_bits" or can an entry in the bitmap be > 1 bit?
> 
I'm not sure I understand what you meant to say here, I'm afraid. The
field encodes the number of elements the bitmap has to accommodate and
deal with. In the (original) xenctl_cpumap case, that was the number of
CPUs... All I'm doing is generalizing that from CPUs to some unspecified
"element". It never was the size of the bitmap in bits, and is not
becoming anything like that after the change.

But again, I did not get the question, so I'm probably not answering
either... :-(

Thanks and Regards,
Dario

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