From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 460A0C2D0EA for ; Wed, 8 Apr 2020 16:07:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F38E1206F5 for ; Wed, 8 Apr 2020 16:07:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="O2VZqDpC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F38E1206F5 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 97A0C8E000D; Wed, 8 Apr 2020 12:07:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 92A6B8E0006; Wed, 8 Apr 2020 12:07:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 819668E000D; Wed, 8 Apr 2020 12:07:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 67B578E0006 for ; Wed, 8 Apr 2020 12:07:31 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 1DAEE181AEF31 for ; Wed, 8 Apr 2020 16:07:31 +0000 (UTC) X-FDA: 76685167902.25.scale61_75fe775fd43c X-HE-Tag: scale61_75fe775fd43c X-Filterd-Recvd-Size: 6685 Received: from mail-pg1-f195.google.com (mail-pg1-f195.google.com [209.85.215.195]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Wed, 8 Apr 2020 16:07:30 +0000 (UTC) Received: by mail-pg1-f195.google.com with SMTP id l14so3535976pgb.1 for ; Wed, 08 Apr 2020 09:07:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=EqYTy5Ki2ftdsDzKpBidXoX+dybhSPikaSHXCZcU+eU=; b=O2VZqDpCb1BgKcwoO3coms9NYMfTPk9fUNL6Zw0PSvHpPZucSjCzQSYPZmiolRFY1L iKDpeNrnhi9sbCtUXZwEiH18pxRNgJUMpsmdh0F3lmV00YQ/cwbcCUgun4DWnO+BcYL+ 3/R20fy57KfPasBEEcGvAtwLs8bmaS1D1wyRb+FTL3tdZtyt31khk2Jllsxvo6le2b4p Zw3dHZKfNLtf7DJjCZ20O8fpU7VDJUqjooD3dwISa+BcXTJRWkg/NPdFr8Cf0JvrY/Gd 5tvAfV8P/f7LV71013D9PucdwQSSGOld4uqSkMxYN68WotnzJQRiIis/Y/N4A3mln/ti x+IA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=EqYTy5Ki2ftdsDzKpBidXoX+dybhSPikaSHXCZcU+eU=; b=hAXGuSov5V4jpP0BaL2LEih7E1Ny9yzH5ddArAkuSXZ1SAGHcqAayGcE/UHOte9Pc8 vACOq0f4IHvjMzDtyXeBMnh0U/TL4+0gtq9Pk4CprgkL5AgiCRql9Wi+XFt81JDlE0JY E8Nsc/JprmlI9D10LHxChndB71OD5HA2LAcN8XXndYZ7e+7Kei2UxcXIbYOd89ZuDanZ qJJOkAPNwoHg9Nu8Fx6vsfskRJiDqMc4Vlg7ZfTP0dO7/JXQMp/69iI2Vn3TQJZ64cBt tlcTwgiDXTickpDF1u4P17iUHvr66i5ZvCjsA2ioOlX5OUjP33MI+Mt0Vz6ZMK94N4yi Oc0g== X-Gm-Message-State: AGi0PuYpwSNBP2OvgsO+0Qk4n/z7WXx/2Wp2eo8DJH8LnCtgxA+74/5y UO34b6U5jwUL9DqHlcLY/P9wbSpN+aFI62aSxtf7Zw== X-Google-Smtp-Source: APiQypIkPGNqbSfLL7J1Ivb4rD0BluVUG8FPE0VVjGzJBizRMfTkhnklSMoV64Aj3nld957uAxe5OND6eoPVbOw4SQc= X-Received: by 2002:a63:cf02:: with SMTP id j2mr7725804pgg.130.1586362049464; Wed, 08 Apr 2020 09:07:29 -0700 (PDT) MIME-Version: 1.0 References: <20200325161249.55095-1-glider@google.com> <20200325161249.55095-26-glider@google.com> In-Reply-To: <20200325161249.55095-26-glider@google.com> From: Andrey Konovalov Date: Wed, 8 Apr 2020 18:07:18 +0200 Message-ID: Subject: Re: [PATCH v5 25/38] kmsan: unpoison |tlb| in arch_tlb_gather_mmu() To: Alexander Potapenko Cc: Vegard Nossum , Dmitry Vyukov , Marco Elver , Linux Memory Management List , Alexander Viro , Andreas Dilger , Andrew Morton , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Christoph Hellwig , Christoph Hellwig , "Darrick J. Wong" , "David S. Miller" , Dmitry Torokhov , Eric Biggers , Eric Dumazet , Eric Van Hensbergen , Greg Kroah-Hartman , Harry Wentland , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jason Wang , Jens Axboe , Marek Szyprowski , Mark Rutland , "Martin K. Petersen" , Martin Schwidefsky , Matthew Wilcox , "Michael S . Tsirkin" , Michal Hocko , Michal Simek , Petr Mladek , Qian Cai , Randy Dunlap , Robin Murphy , Sergey Senozhatsky , Steven Rostedt , Takashi Iwai , "Theodore Ts'o" , Thomas Gleixner , Vasily Gorbik , Wolfram Sang Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Mar 25, 2020 at 5:14 PM wrote: > > This is a hack to reduce stackdepot pressure. > > struct mmu_gather contains 7 1-bit fields packed into a 32-bit unsigned > int value. The remaining 25 bits remain uninitialized and are never used, > but KMSAN updates the origin for them in zap_pXX_range() in mm/memory.c, > thus creating very long origin chains. This is technically correct, but > consumes too much memory. > > Unpoisoning the whole structure will prevent creating such chains. > > Signed-off-by: Alexander Potapenko > To: Alexander Potapenko > Cc: Vegard Nossum > Cc: Dmitry Vyukov > Cc: Marco Elver > Cc: Andrey Konovalov > Cc: linux-mm@kvack.org Reviewed-by: Andrey Konovalov > > --- > > v4: > - removed a TODO, updated patch description > > Change-Id: I22a201e7e4f67ed74f8129072f12e5351b26103a > --- > mm/mmu_gather.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c > index a3538cb2bcbee..d3d57c276e301 100644 > --- a/mm/mmu_gather.c > +++ b/mm/mmu_gather.c > @@ -1,6 +1,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -264,6 +265,15 @@ void tlb_flush_mmu(struct mmu_gather *tlb) > void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, > unsigned long start, unsigned long end) > { > + /* > + * struct mmu_gather contains 7 1-bit fields packed into a 32-bit > + * unsigned int value. The remaining 25 bits remain uninitialized > + * and are never used, but KMSAN updates the origin for them in > + * zap_pXX_range() in mm/memory.c, thus creating very long origin > + * chains. This is technically correct, but consumes too much memory. > + * Unpoisoning the whole structure will prevent creating such chains. > + */ > + kmsan_unpoison_shadow(tlb, sizeof(*tlb)); > tlb->mm = mm; > > /* Is it from 0 to ~0? */ > -- > 2.25.1.696.g5e7596f4ac-goog >