Re: [PATCH v6 09/15] xen/page_alloc: introduce preserved page flags macro

[Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>]

Hi Jan,

On Thu, Feb 1, 2024 at 3:24 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 29.01.2024 18:18, Carlo Nonato wrote:
> > PGC_static and PGC_extra are flags that needs to be preserved when assigning
> > a page. Define a new macro that groups those flags and use it instead of
> > or'ing every time.
>
> While here you say where the "preserving" applies, ...
>
> > --- a/xen/common/page_alloc.c
> > +++ b/xen/common/page_alloc.c
> > @@ -157,6 +157,8 @@
> >  #define PGC_static 0
> >  #endif
> >
> > +#define PGC_preserved (PGC_extra | PGC_static)
>
> ... nothing is said here. From the earlier version I also seem to recall
> that the constant was then used outside of assign_pages(). That would
> then mean amending whatever comment would be added here.

Yes, but it was used in places where the name didn't fit (to stop merging in
free_heap_pages()) and so I thought it would've been better to use the
constant only for one of the two concepts: only for preserved flags in
assign_pages().

Are you suggesting adding a comment to this #define to clarify its usage?

Thanks.

> Jan