Re: [Xen-devel] [PATCH v5 03/10] IOMMU/MMU: enhance the call trees of IOMMU unmapping and mapping

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> "Xu, Quan" <quan.xu@xxxxxxxxx> 05/26/16 3:42 AM >>>
>On May 26, 2016 12:02 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> >>> On 25.05.16 at 17:34, <quan.xu@xxxxxxxxx> wrote:
>> > On May 23, 2016 10:19 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> >> >>> On 18.05.16 at 10:08, <quan.xu@xxxxxxxxx> wrote:
>> >> > +                                        unsigned long type,
>> >> > +                                        int preemptible)
>> >> >  {
>> >> >      unsigned long nx, x, y = page->u.inuse.type_info;
>> >> > -    int rc = 0;
>> >> > +    int rc = 0, ret = 0;
>> >> >
>> >> >      ASSERT(!(type & ~(PGT_type_mask | PGT_pae_xen_l2)));
>> >> >
>> >> > @@ -2578,11 +2579,11 @@ static int __get_page_type(struct page_info
>> >> *page, unsigned long type,
>> >> >          if ( d && is_pv_domain(d) && unlikely(need_iommu(d)) )
>> >> >          {
>> >> >              if ( (x & PGT_type_mask) == PGT_writable_page )
>> >> > -                iommu_unmap_page(d, mfn_to_gmfn(d, page_to_mfn(page)));
>> >> > +                ret = iommu_unmap_page(d, mfn_to_gmfn(d,
>> >> > + page_to_mfn(page)));
>> >> >              else if ( type == PGT_writable_page )
>> >> > -                iommu_map_page(d, mfn_to_gmfn(d, page_to_mfn(page)),
>> >> > -                               page_to_mfn(page),
>> >> > -                               IOMMUF_readable|IOMMUF_writable);
>> >> > +                ret = iommu_map_page(d, mfn_to_gmfn(d, 
>> >> > page_to_mfn(page)),
>> >> > +                                     page_to_mfn(page),
>> >> > +
>> >> > + IOMMUF_readable|IOMMUF_writable);
>> >> >          }
>> >> >      }
>> >> >
>> >> > @@ -2599,6 +2600,9 @@ static int __get_page_type(struct page_info
>> >> *page, unsigned long type,
>> >> >      if ( (x & PGT_partial) && !(nx & PGT_partial) )
>> >> >          put_page(page);
>> >> >
>> >> > +    if ( !rc )
>> >> > +        rc = ret;
>> >>
>> >> I know I've seen this a couple of time already, but with the special
>> >> purpose of "ret" I really wonder whether a more specific name
>> >> wouldn't be warranted - e.g. "iommu_rc" or "iommu_ret".
>> >
>> >
>> > rc is return value for this function, and no directly association with
>> > IOMMU related code ( rc is only for alloc_page_type() ).
>> > So the rc cannot be "iommu_rc"..
>> >
>> > ret can be "iommu_ret", but I think the pair 'rc' / 'ret' may look good.
>> 
>> Well, I'm not entirely opposed to keeping the names, but I continue to think
>> that while at the call sites the shorter name is reasonable, it is quite a 
>> bit less
>> clear at the point where you conditionally update rc.
>
>I am open to it. What about 'rc' / 'iommu_ret' ?

As that matches one of the two options I had suggested, I don't really see why
you ask back.

Jan


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