From patchwork Tue Sep 15 03:21:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Herbert Xu X-Patchwork-Id: 11775677 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8149192C for ; Tue, 15 Sep 2020 07:07:31 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2AFC0206C9 for ; Tue, 15 Sep 2020 07:07:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2AFC0206C9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gondor.apana.org.au Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4468289ECB; Tue, 15 Sep 2020 07:07:19 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org X-Greylist: delayed 1035 seconds by postgrey-1.36 at gabe; Tue, 15 Sep 2020 03:40:58 UTC Received: from fornost.hmeau.com (helcar.hmeau.com [216.24.177.18]) by gabe.freedesktop.org (Postfix) with ESMTPS id 806436E836; Tue, 15 Sep 2020 03:40:58 +0000 (UTC) Received: from gwarestrin.arnor.me.apana.org.au ([192.168.0.7]) by fornost.hmeau.com with smtp (Exim 4.92 #5 (Debian)) id 1kI1XG-0005IE-1y; Tue, 15 Sep 2020 13:21:39 +1000 Received: by gwarestrin.arnor.me.apana.org.au (sSMTP sendmail emulation); Tue, 15 Sep 2020 13:21:37 +1000 Date: Tue, 15 Sep 2020 13:21:37 +1000 From: Herbert Xu To: Linus Torvalds Subject: [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally Message-ID: <20200915032137.GA25655@gondor.apana.org.au> References: <20200914204209.256266093@linutronix.de> <871rj4owfn.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Mailman-Approved-At: Tue, 15 Sep 2020 07:07:18 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , Peter Zijlstra , Sebastian Andrzej Siewior , Lai Jiangshan , dri-devel , Ben Segall , Linux-MM , linux-hexagon@vger.kernel.org, Will Deacon , Ingo Molnar , Anton Ivanov , linux-arch , Vincent Guittot , Brian Cain , Richard Weinberger , Russell King , Ard Biesheuvel , David Airlie , Ingo Molnar , Geert Uytterhoeven , Mel Gorman , intel-gfx , Matt Turner , Valentin Schneider , linux-xtensa@linux-xtensa.org, Shuah Khan , "Paul E. McKenney" , "open list:KERNEL SELFTEST FRAMEWORK" , Jeff Dike , linux-um , Josh Triplett , Steven Rostedt , rcu@vger.kernel.org, linux-m68k , Ivan Kokshaysky , Rodrigo Vivi , Thomas Gleixner , Dietmar Eggemann , Linux ARM , Richard Henderson , Chris Zankel , Max Filippov , LKML , alpha , Mathieu Desnoyers , Andrew Morton , Daniel Bristot de Oliveira Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 Signed-off-by: Herbert Xu 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);