From: Herbert Xu <herbert@gondor.apana.org.au>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ard Biesheuvel <ardb@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
Subject: [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally
Date: Tue, 15 Sep 2020 13:30:24 +1000 [thread overview]
Message-ID: <20200915033024.GB25789@gondor.apana.org.au> (raw)
In-Reply-To: <CAHk-=wjOV6f_ddg+QVCF6RUe+pXPhSR2WevnNyOs9oT+q2ihEA@mail.gmail.com>
I trimmed the cc as the mailing lists appear to be blocking this
email because of it.
On Mon, Sep 14, 2020 at 03:37:49PM -0700, Linus Torvalds wrote:
>
> So it _looks_ like this code started using kmap() - probably back when
> kmap_atomic() was so cumbersome to use - and was then converted
> (conditionally) to kmap_atomic() rather than just changed whole-sale.
> Is there actually something that wants to use those sg_miter functions
> and sleep?
I dug up the old zinc patch submissions and this wasn't present at
all in the original. The original zinc code used blkcipher_walk
which unconditinoally does kmap_atomic.
So it's only the SG miter conversion that introduced this change,
which appears to be a simple oversight (I think Ard was working on
latency issues at that time, perhaps he was worried about keeping
preemption off unnecessarily).
---8<---
There is no reason for the chacha20poly1305 SG miter code to use
kmap instead of kmap_atomic as the critical section doesn't sleep
anyway. So we can simply get rid of the preemptible check and
set SG_MITER_ATOMIC unconditionally.
Even if we need to reenable preemption to lower latency we should
be doing that by interrupting the SG miter walk rather than using
kmap.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/lib/crypto/chacha20poly1305.c b/lib/crypto/chacha20poly1305.c
index 431e04280332..5850f3b87359 100644
--- a/lib/crypto/chacha20poly1305.c
+++ b/lib/crypto/chacha20poly1305.c
@@ -251,9 +251,7 @@ bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src,
poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));
}
- flags = SG_MITER_TO_SG;
- if (!preemptible())
- flags |= SG_MITER_ATOMIC;
+ flags = SG_MITER_TO_SG | SG_MITER_ATOMIC;
sg_miter_start(&miter, src, sg_nents(src), flags);
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2020-09-15 3:30 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200914204209.256266093@linutronix.de>
[not found] ` <20200914204441.579902354@linutronix.de>
2020-09-15 16:10 ` [patch 06/13] locking/bitspinlock: Clenaup PREEMPT_COUNT leftovers Will Deacon
[not found] ` <20200914204441.375753691@linutronix.de>
2020-09-15 16:11 ` [patch 04/13] lockdep: " Will Deacon
[not found] ` <CAHk-=win80rdof8Pb=5k6gT9j_v+hz-TQzKPVastZDvBe9RimQ@mail.gmail.com>
2020-09-15 17:25 ` [patch 00/13] preempt: Make preempt count unconditional Paul E. McKenney
[not found] ` <871rj4owfn.fsf@nanos.tec.linutronix.de>
[not found] ` <CAHk-=wj0eUuVQ=hRFZv_nY7g5ZLt7Fy3K7SMJL0ZCzniPtsbbg@mail.gmail.com>
[not found] ` <CAHk-=wjOV6f_ddg+QVCF6RUe+pXPhSR2WevnNyOs9oT+q2ihEA@mail.gmail.com>
2020-09-15 3:30 ` Herbert Xu [this message]
2020-09-15 6:03 ` [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally Ard Biesheuvel
2020-09-15 6:40 ` Herbert Xu
2020-09-15 6:45 ` Linus Torvalds
2020-09-15 6:55 ` Linus Torvalds
2020-09-15 7:05 ` Herbert Xu
2020-09-15 7:10 ` Ard Biesheuvel
2020-09-15 9:34 ` Thomas Gleixner
2020-09-15 10:02 ` Ard Biesheuvel
2020-09-15 10:05 ` Herbert Xu
2020-09-15 10:08 ` Ard Biesheuvel
2020-09-15 10:10 ` Herbert Xu
2020-09-15 19:04 ` Thomas Gleixner
2020-09-15 7:08 ` Ard Biesheuvel
2020-09-15 6:20 ` [patch 00/13] preempt: Make preempt count unconditional Ard Biesheuvel
[not found] ` <20200915062253.GA26275@gondor.apana.org.au>
2020-09-15 6:39 ` Linus Torvalds
2020-09-15 7:24 ` Thomas Gleixner
2020-09-15 17:29 ` Linus Torvalds
2020-09-15 8:39 ` Thomas Gleixner
2020-09-15 17:35 ` Linus Torvalds
2020-09-15 19:57 ` Thomas Gleixner
2020-09-16 18:34 ` Linus Torvalds
2020-09-16 7:37 ` Daniel Vetter
2020-09-16 15:29 ` Paul E. McKenney
2020-09-16 18:32 ` Linus Torvalds
2020-09-16 20:43 ` Paul E. McKenney
2020-09-17 6:38 ` Ard Biesheuvel
2020-09-16 20:29 ` Daniel Vetter
2020-09-16 20:58 ` Paul E. McKenney
2020-09-16 21:43 ` Daniel Vetter
2020-09-16 22:39 ` Paul E. McKenney
2020-09-17 7:52 ` Daniel Vetter
2020-09-17 16:28 ` Paul E. McKenney
2020-09-29 8:19 ` Michal Hocko
2020-09-29 8:19 ` Michal Hocko
2020-09-29 8:20 ` Michal Hocko
2020-09-29 8:21 ` Michal Hocko
2020-09-29 8:23 ` Michal Hocko
2020-09-29 9:00 ` Daniel Vetter
2020-09-29 14:54 ` Michal Hocko
2020-09-16 19:23 ` Matthew Wilcox
2020-09-16 20:48 ` Paul E. McKenney
[not found] ` <20200914204441.268144917@linutronix.de>
2020-09-16 10:56 ` [patch 03/13] preempt: Clenaup PREEMPT_COUNT leftovers Valentin Schneider
[not found] ` <20200914204441.794954043@linutronix.de>
2020-09-16 10:56 ` [patch 08/13] sched: " Valentin Schneider
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