Re: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits

Charlie Jenkins
2024-09-09T19:07:32Z

On Fri, Sep 06, 2024 at 04:59:40PM +1000, Michael Ellerman wrote:
> Charlie Jenkins <charlie@rivosinc.com> writes:
> > Create a personality flag ADDR_LIMIT_47BIT to support applications
> > that wish to transition from running in environments that support at
> > most 47-bit VAs to environments that support larger VAs. This
> > personality can be set to cause all allocations to be below the 47-bit
> > boundary. Using MAP_FIXED with mmap() will bypass this restriction.
> >
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> > include/uapi/linux/personality.h | 1 +
> > mm/mmap.c | 3 +++
> > 2 files changed, 4 insertions(+)
> >
> > diff --git a/include/uapi/linux/personality.h b/include/uapi/linux/personality.h
> > index 49796b7756af..cd3b8c154d9b 100644
> > --- a/include/uapi/linux/personality.h
> > +++ b/include/uapi/linux/personality.h
> > @@ -22,6 +22,7 @@ enum {
> > WHOLE_SECONDS = 0x2000000,
> > STICKY_TIMEOUTS = 0x4000000,
> > ADDR_LIMIT_3GB = 0x8000000,
> > + ADDR_LIMIT_47BIT = 0x10000000,
> > };
>
> I wonder if ADDR_LIMIT_128T would be clearer?
>

I don't follow, what does 128T represent?

> Have you looked at writing an update for the personality(2) man page? :)

I will write an update to the man page if this patch is approved!

>
> cheers

- Charlie