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From: Alexander Potapenko <glider@google.com>
To: Marco Elver <elver@google.com>, Michal Hocko <mhocko@suse.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Dmitry Vyukov <dvyukov@google.com>,
	Linux Memory Management List <linux-mm@kvack.org>,
	 Al Viro <viro@zeniv.linux.org.uk>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	 Andrey Konovalov <andreyknvl@google.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	 Andy Lutomirski <luto@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	 Arnd Bergmann <arnd@arndb.de>,
	Christoph Hellwig <hch@infradead.org>,
	Christoph Hellwig <hch@lst.de>,
	 "Darrick J. Wong" <darrick.wong@oracle.com>,
	David Miller <davem@davemloft.net>,
	 Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Eric Biggers <ebiggers@google.com>,
	 Eric Dumazet <edumazet@google.com>,
	Eric Van Hensbergen <ericvh@gmail.com>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Harry Wentland <harry.wentland@amd.com>,
	 Herbert Xu <herbert@gondor.apana.org.au>,
	Ilya Leoshkevich <iii@linux.ibm.com>,
	 Ingo Molnar <mingo@elte.hu>, Jason Wang <jasowang@redhat.com>,
	Jens Axboe <axboe@kernel.dk>,
	 Marek Szyprowski <m.szyprowski@samsung.com>,
	Mark Rutland <mark.rutland@arm.com>,
	 "Martin K . Petersen" <martin.petersen@oracle.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	 Matthew Wilcox <willy@infradead.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Michal Simek <monstr@monstr.eu>,  Petr Mladek <pmladek@suse.com>,
	Qian Cai <cai@lca.pw>, Randy Dunlap <rdunlap@infradead.org>,
	 Robin Murphy <robin.murphy@arm.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	 Steven Rostedt <rostedt@goodmis.org>,
	Takashi Iwai <tiwai@suse.com>, "Theodore Ts'o" <tytso@mit.edu>,
	 Thomas Gleixner <tglx@linutronix.de>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH RFC v3 06/36] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW
Date: Tue, 3 Dec 2019 13:57:48 +0100
Message-ID: <CAG_fn=X7wsgeD1Jqs9kEDf5Tk8VumHDH9UyUXVhkp35KChWDQw@mail.gmail.com> (raw)
In-Reply-To: <CANpmjNNJuWvN2J9CxGuvkKJZfOsJhH5f13t9fS2zMztNOGU6KQ@mail.gmail.com>

On Wed, Nov 27, 2019 at 3:48 PM Marco Elver <elver@google.com> wrote:
>
> On Fri, 22 Nov 2019 at 12:26, <glider@google.com> wrote:
> >
> > This flag is to be used by KMSAN runtime to mark that newly created
> > memory pages don't need KMSAN metadata backing them.
> >
> > Signed-off-by: Alexander Potapenko <glider@google.com>
> > To: Alexander Potapenko <glider@google.com>
> > Cc: Vegard Nossum <vegard.nossum@oracle.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: linux-mm@kvack.org
> >
> > ---
> > We can't decide what to do here:
> >  - do we need to conditionally define ___GFP_NO_KMSAN_SHADOW depending on
> >    CONFIG_KMSAN like LOCKDEP does?
> >  - if KMSAN is defined, and LOCKDEP is not, do we want to "compactify" the GFP
> >    bits?
>
> A maintainer would know the real answer, but this is my guess: making
> the behaviour not change without KMSAN would probably be better. It
> would require some ifdef trickery to deal with LOCKDEP on/off case
> though.
I actually find it quite unfortunate that LOCKDEP has this on/off case.
It's already inconvenient to add a new GFP flag past ___GFP_NOLOCKDEP,
as its value will be depending on this blinking LOCKDEP bit.
Now imagine someone wants to add a second GFP flag that can be
disabled similarly to LOCKDEP - there'll be even more hassle counting
which bits are present.

Michal, do you think it's possible to make __GFP_BITS_SHIFT
independent from CONFIG_LOCKDEP?

> > Change-Id: If5d0352fd5711ad103328e2c185eb885e826423a
> > ---
> >  include/linux/gfp.h | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index fb07b503dc45..b4e7963cd94b 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -44,6 +44,7 @@ struct vm_area_struct;
> >  #else
> >  #define ___GFP_NOLOCKDEP       0
> >  #endif
>
> Since this change unconditionally changes GFP_BITS_SHIFT to 25, the
> #ifdef for GFP_NOLOCKDEP could also go away -- but: see above.
>
> > +#define ___GFP_NO_KMSAN_SHADOW  0x1000000u
> >  /* If the above are modified, __GFP_BITS_SHIFT may need updating */
> >
> >  /*
> > @@ -212,12 +213,13 @@ struct vm_area_struct;
> >  #define __GFP_NOWARN   ((__force gfp_t)___GFP_NOWARN)
> >  #define __GFP_COMP     ((__force gfp_t)___GFP_COMP)
> >  #define __GFP_ZERO     ((__force gfp_t)___GFP_ZERO)
> > +#define __GFP_NO_KMSAN_SHADOW  ((__force gfp_t)___GFP_NO_KMSAN_SHADOW)
>
> Should this be ordered after __GFP_NOLOCKDEP with a brief comment what
> it does?  All of these up to __GFP_ZERO have a doc comment above.
>
> >  /* Disable lockdep for GFP context tracking */
> >  #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
> >
> >  /* Room for N __GFP_FOO bits */
> > -#define __GFP_BITS_SHIFT (23 + IS_ENABLED(CONFIG_LOCKDEP))
> > +#define __GFP_BITS_SHIFT (25)
> >  #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
> >
> >  /**
> > --
> > 2.24.0.432.g9d3f5f5b63-goog
> >



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg


  reply index

Thread overview: 120+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-22 11:25 [PATCH RFC v3 00/36] Add KernelMemorySanitizer infrastructure glider
2019-11-22 11:25 ` [PATCH RFC v3 01/36] stackdepot: check depot_index before accessing the stack slab glider
2019-11-27 14:22   ` Marco Elver
2019-11-22 11:25 ` [PATCH RFC v3 02/36] stackdepot: build with -fno-builtin glider
2019-11-27 14:22   ` Marco Elver
2019-11-22 11:25 ` [PATCH RFC v3 03/36] kasan: stackdepot: move filter_irq_stacks() to stackdepot.c glider
2019-11-27 14:22   ` Marco Elver
2019-11-27 14:56     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 04/36] stackdepot: reserve 5 extra bits in depot_stack_handle_t glider
2019-11-27 14:23   ` Marco Elver
2019-11-22 11:25 ` [PATCH RFC v3 05/36] kmsan: add ReST documentation glider
2019-11-27 14:22   ` Marco Elver
2019-12-03 12:42     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 06/36] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW glider
2019-11-27 14:48   ` Marco Elver
2019-12-03 12:57     ` Alexander Potapenko [this message]
2019-11-22 11:25 ` [PATCH RFC v3 07/36] kmsan: introduce __no_sanitize_memory and __SANITIZE_MEMORY__ glider
2019-11-28 13:13   ` Marco Elver
2019-11-29 16:09   ` Andrey Konovalov
2019-12-16 11:35     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 08/36] kmsan: reduce vmalloc space glider
2019-11-28 13:30   ` Marco Elver
2019-11-22 11:25 ` [PATCH RFC v3 09/36] kmsan: add KMSAN bits to struct page and struct task_struct glider
2019-11-28 13:44   ` Marco Elver
2019-11-28 14:05     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 10/36] kmsan: add KMSAN runtime glider
2019-11-24 19:44   ` Wolfram Sang
2019-11-25  9:14     ` Alexander Potapenko
2019-11-29 16:07   ` Marco Elver
2019-12-19 14:16     ` Alexander Potapenko
2019-12-02 15:39   ` Andrey Konovalov
2019-12-20 18:58     ` Alexander Potapenko
2019-12-03 14:34   ` Andrey Konovalov
2019-11-22 11:25 ` [PATCH RFC v3 11/36] kmsan: stackdepot: don't allocate KMSAN metadata for stackdepot glider
2019-11-29 14:52   ` Andrey Konovalov
2019-12-03 14:27     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 12/36] kmsan: define READ_ONCE_NOCHECK() glider
2019-12-02 10:03   ` Marco Elver
2019-12-03 12:45     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 13/36] kmsan: make READ_ONCE_TASK_STACK() return initialized values glider
2019-12-02 10:07   ` Marco Elver
2019-12-05 15:52     ` Alexander Potapenko
2019-11-22 11:25 ` [PATCH RFC v3 14/36] kmsan: x86: sync metadata pages on page fault glider
2019-11-22 11:26 ` [PATCH RFC v3 15/36] kmsan: add tests for KMSAN glider
2019-11-29 14:14   ` Andrey Konovalov
2019-12-05 14:30     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 16/36] crypto: kmsan: disable accelerated configs under KMSAN glider
2019-12-02 13:25   ` Marco Elver
2019-12-05 14:51     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 17/36] kmsan: x86: disable UNWINDER_ORC " glider
2019-12-02 13:30   ` Marco Elver
2019-11-22 11:26 ` [PATCH RFC v3 18/36] kmsan: disable LOCK_DEBUGGING_SUPPORT glider
2019-12-02 13:33   ` Marco Elver
2019-12-03 14:34     ` Alexander Potapenko
2019-12-03 15:00       ` Qian Cai
2019-12-03 15:14         ` Alexander Potapenko
2019-12-03 18:02           ` Qian Cai
2019-12-03 18:38           ` Steven Rostedt
2019-12-04  8:41             ` Alexander Potapenko
2019-12-04 12:22               ` Petr Mladek
2019-12-04 13:12                 ` Qian Cai
2019-12-04 16:24                   ` Alexander Potapenko
2019-12-04 18:03                     ` Qian Cai
2019-11-22 11:26 ` [PATCH RFC v3 20/36] kmsan: x86: increase stack sizes in KMSAN builds glider
2019-12-02 14:31   ` Marco Elver
2019-11-22 11:26 ` [PATCH RFC v3 21/36] kmsan: disable KMSAN instrumentation for certain kernel parts glider
2019-11-29 15:07   ` Andrey Konovalov
2019-12-10 10:35     ` Alexander Potapenko
2019-12-10 12:38       ` Alexander Potapenko
2019-12-10 12:43       ` Qian Cai
2019-11-22 11:26 ` [PATCH RFC v3 22/36] kmsan: mm: call KMSAN hooks from SLUB code glider
2019-12-02 15:36   ` Marco Elver
2019-12-10 12:07     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 23/36] kmsan: call KMSAN hooks where needed glider
2019-11-26 10:17   ` Petr Mladek
2019-11-26 10:52     ` Alexander Potapenko
2019-11-29 16:21   ` Andrey Konovalov
2019-12-16 11:30     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 24/36] kmsan: disable instrumentation of certain functions glider
2019-11-29 14:59   ` Andrey Konovalov
2019-12-18 10:02     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 25/36] kmsan: unpoison |tlb| in arch_tlb_gather_mmu() glider
2019-11-29 15:08   ` Andrey Konovalov
2019-12-03 14:19     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 26/36] kmsan: use __msan_memcpy() where possible glider
2019-11-29 15:13   ` Andrey Konovalov
2019-12-05 15:46     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 27/36] kmsan: hooks for copy_to_user() and friends glider
2019-11-29 15:34   ` Andrey Konovalov
2019-12-05 16:00     ` Alexander Potapenko
2019-12-05 16:44       ` Andrey Konovalov
2019-12-11 14:22         ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 28/36] kmsan: enable KMSAN builds glider
2019-11-29 15:55   ` Andrey Konovalov
2019-12-11 12:51     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 29/36] kmsan: handle /dev/[u]random glider
2019-11-22 11:26 ` [PATCH RFC v3 30/36] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg() glider
2019-11-22 11:26 ` [PATCH RFC v3 31/36] kmsan: disable strscpy() optimization under KMSAN glider
2019-12-02 15:51   ` Marco Elver
2019-12-02 16:23     ` Alexander Potapenko
2019-12-03 11:19       ` Alexander Potapenko
2019-12-03 11:24         ` Marco Elver
2019-12-03 11:27           ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 32/36] kmsan: add iomap support glider
2019-12-03 12:50   ` Marco Elver
2019-12-03 14:07     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 33/36] kmsan: dma: unpoison memory mapped by dma_direct_map_page() glider
2019-11-22 11:26 ` [PATCH RFC v3 34/36] kmsan: disable physical page merging in biovec glider
2019-12-03 12:54   ` Marco Elver
2019-12-03 13:38     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 35/36] kmsan: ext4: skip block merging logic in ext4_mpage_readpages for KMSAN glider
2019-11-25 16:05   ` Robin Murphy
2019-11-25 17:03     ` Alexander Potapenko
2019-12-03 14:22   ` Marco Elver
2019-12-05 14:31     ` Alexander Potapenko
2019-11-22 11:26 ` [PATCH RFC v3 36/36] net: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN glider
2019-12-03 14:17   ` Marco Elver
2019-12-05 14:37     ` Alexander Potapenko
2019-11-29 14:39 ` [PATCH RFC v3 00/36] Add KernelMemorySanitizer infrastructure Marco Elver
2019-12-02 16:02   ` Alexander Potapenko

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