[PATCH mm v3 28/38] kasan, page_alloc: allow skipping memory init for HW_TAGS

[Andrey Konovalov]

On Tue, Dec 14, 2021 at 7:00 PM Marco Elver <elver at google.com> wrote:
>
> On Mon, Dec 13, 2021 at 10:54PM +0100, andrey.konovalov at linux.dev wrote:
> > From: Andrey Konovalov <andreyknvl at google.com>
> >
> > Add a new GFP flag __GFP_SKIP_ZERO that allows to skip memory
> > initialization. The flag is only effective with HW_TAGS KASAN.
> [...]
> > - * is being zeroed (either via __GFP_ZERO or via init_on_alloc).
> > + * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that
> > + * __GFP_SKIP_ZERO is not set).
> > + *
> > + * %__GFP_SKIP_ZERO makes page_alloc skip zeroing memory.
> > + * Only effective when HW_TAGS KASAN is enabled.
> >   *
> >   * %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation.
> >   * Only effective in HW_TAGS mode.
> > @@ -242,6 +247,7 @@ struct vm_area_struct;
> >  #define __GFP_COMP   ((__force gfp_t)___GFP_COMP)
> >  #define __GFP_ZERO   ((__force gfp_t)___GFP_ZERO)
> >  #define __GFP_ZEROTAGS       ((__force gfp_t)___GFP_ZEROTAGS)
> > +#define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO)
> >  #define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON)
> >  #define __GFP_SKIP_KASAN_POISON   ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
> >
> > @@ -249,7 +255,7 @@ struct vm_area_struct;
> >  #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
> >
> >  /* Room for N __GFP_FOO bits */
> > -#define __GFP_BITS_SHIFT (26 + IS_ENABLED(CONFIG_LOCKDEP))
> > +#define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP))
>
> You're adding several new flags, I think you should also make a
> corresponding change to include/trace/events/mmflags.h?
>
> At least __GFP_SKIP_KASAN_POISON is currently in there.

Indeed, will fix in v4. Thanks!