Re: [RFC PATCH v4 2/9] tools headers: Add a macro to get HUGETLB page sizes for mmap

[wangyanan (Y)]

On 2021/3/12 19:14, Andrew Jones wrote:
> On Tue, Mar 02, 2021 at 08:57:44PM +0800, Yanan Wang wrote:
> > We know that if a system supports multiple hugetlb page sizes,
> > the desired hugetlb page size can be specified in bits [26:31]
> > of the flag arguments. The value in these 6 bits will be the
> > shift of each hugetlb page size.
> >
> > So add a macro to get the page size shift and then calculate the
> > corresponding hugetlb page size, using flag x.
> >
> > Cc: Ben Gardon <bgardon@xxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Suggested-by: Ben Gardon <bgardon@xxxxxxxxxx>
> > Signed-off-by: Yanan Wang <wangyanan55@xxxxxxxxxx>
> > Reviewed-by: Ben Gardon <bgardon@xxxxxxxxxx>
> > ---
> >   include/uapi/linux/mman.h       | 2 ++
> >   tools/include/uapi/linux/mman.h | 2 ++
> >   2 files changed, 4 insertions(+)
> >
> > diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
> > index f55bc680b5b0..8bd41128a0ee 100644
> > --- a/include/uapi/linux/mman.h
> > +++ b/include/uapi/linux/mman.h
> > @@ -41,4 +41,6 @@
> >   #define MAP_HUGE_2GB	HUGETLB_FLAG_ENCODE_2GB
> >   #define MAP_HUGE_16GB	HUGETLB_FLAG_ENCODE_16GB
> >   
> > +#define MAP_HUGE_PAGE_SIZE(x) (1 << ((x >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK))
> Needs to be '1ULL' to avoid shift overflow when given MAP_HUGE_16GB.
Thanks, drew. Will fix it.
> Thanks,
> drew
>
> > +
> >   #endif /* _UAPI_LINUX_MMAN_H */
> > diff --git a/tools/include/uapi/linux/mman.h b/tools/include/uapi/linux/mman.h
> > index f55bc680b5b0..8bd41128a0ee 100644
> > --- a/tools/include/uapi/linux/mman.h
> > +++ b/tools/include/uapi/linux/mman.h
> > @@ -41,4 +41,6 @@
> >   #define MAP_HUGE_2GB	HUGETLB_FLAG_ENCODE_2GB
> >   #define MAP_HUGE_16GB	HUGETLB_FLAG_ENCODE_16GB
> >   
> > +#define MAP_HUGE_PAGE_SIZE(x) (1 << ((x >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK))
> > +
> >   #endif /* _UAPI_LINUX_MMAN_H */
> > --
> > 2.23.0
> .