Re: [Xen-devel] [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 10 Aug 2015, David Vrabel wrote:
> On 10/08/15 13:03, Stefano Stabellini wrote:
> > On Fri, 7 Aug 2015, Julien Grall wrote:
> >> -  rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap_range, &xatp);
> >> -  return rc < 0 ? rc : err;
> >> +  for (i = 0; i < nr_gfn; i++) {
> >> +          if ((i % XEN_PFN_PER_PAGE) == 0) {
> >> +                  page = pages[i / XEN_PFN_PER_PAGE];
> > 
> > If this function is going to be called very frequently you might want to
> > consider using a shift instead.
> > 
> >     page = pages[i >> 4];
> > 
> > With an appropriate macro of course.
> 
> This change isn't necessary.  Compilers already turn divides into
> suitable shifts.

The ARM compiler I used last time I tested this did not, but that was 1
or 2 years ago. In any case to be clear this change is not required.

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