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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08B26C30658 for ; Tue, 2 Jul 2024 18:36:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 35A316B008A; Tue, 2 Jul 2024 14:36:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 309926B008C; Tue, 2 Jul 2024 14:36:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D1576B0092; Tue, 2 Jul 2024 14:36:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 018496B008A for ; Tue, 2 Jul 2024 14:36:00 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 66DA91604AD for ; Tue, 2 Jul 2024 18:36:00 +0000 (UTC) X-FDA: 82295666880.08.889707F Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf01.hostedemail.com (Postfix) with ESMTP id 9B70C4001C for ; Tue, 2 Jul 2024 18:35:57 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=zef7oasD; spf=pass (imf01.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1719945346; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2yrODVNogFyK5302QTyasOURBpJYoqxZf0s8KNk9+8k=; b=YA0cNRgf7AqWpgw/3K/Zi2AbQWt4XlhV+03wocXjrTPBCtC1ZH5LY6u81mD2/lmAitjerS LTsgDy6UneCS9VBTAAwpek2n2L+SRjw+h7aeByEbpzEb9FeVTkfUvbu78ji8noEU08FENi WWScVVpujf08KynpsgUgyw5J3gS7R+g= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=zef7oasD; spf=pass (imf01.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1719945346; a=rsa-sha256; cv=none; b=EvRgmr4OtAzZBXs+kLITEMUT4eRXfak/5mfeC2UUmMMq4MwsXiK0HBFlDVg952ixhEG2gj oPW8co1RqT8kH6c4SshyF6ZGnw1rvzMsGRsoA9f4gzzK3TEeyLkntsN0ULADgqOW12Re/u 4mHTsLTwhzFiRvVRTjNzA/7p3j5I5O8= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 4E14461F72; Tue, 2 Jul 2024 18:35:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8CE57C116B1; Tue, 2 Jul 2024 18:35:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1719945356; bh=LQa0boYAjyiQy2XLCVd6hOtBE8EViR0thVWazO0ORBE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=zef7oasDBBFb8JoFScauVEm3d31GuSk9PSFVdwIdGlqkzeoqssuhuGZVKJF59/a3z XiI4qE9zGQyfOMiYSRRBwZ5h5EOrBlp1BUtYABxU57cIgZ7bKctUMrg4FC12YMnVvD g2Lrf9YduwMjgojynKmmrIryRaYjPiwTu4I7fezM= Date: Tue, 2 Jul 2024 11:35:54 -0700 From: Andrew Morton To: Yosry Ahmed Cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , "Kirill A. Shutemov" , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH v3 0/3] x86/mm: LAM fixups and cleanups Message-Id: <20240702113554.2471f000055f3c717fced4f5@linux-foundation.org> In-Reply-To: References: <20240702132139.3332013-1-yosryahmed@google.com> <20240702103628.61879ef17b9b01305515c634@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9B70C4001C X-Stat-Signature: i3ydaa6wzcst4iprj6h85pwpuxedmact X-HE-Tag: 1719945357-130152 X-HE-Meta: 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 1Hq+pzmg wzhiTPdFDaZV5bB2DM7ETc8DPj/eK4bPTuddNC+qk663ZB9gRf0IadjtQeFQPtdqsIvIvTqDwnsi3GiiDpsuHxdhNHcPSuMWnjapg+omvcUEjCdl3uq7N4OUhNhpVIcBHUSQSlBIv+VJ0zLKMVcJ5oQVZYf+TsvA165RY0Ehnl9EmWwqn2pOR04MzfIm77O/dlCbH+dpJafJk82Jmz/FTzyzHcBaHJyNYLYlwj7m5sRXAsdMRBgUZYbX0u7iRrYM+C83rw7Z7y1muWWumphzZ/W76RdL4q5IUfAOnBPpbVTd7FlnHY2ULnWQh67zieTJe22uayQ3kBEfc1kC4JCj2+pTL5Q== 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: List-Subscribe: List-Unsubscribe: On Tue, 2 Jul 2024 10:39:03 -0700 Yosry Ahmed wrote: > On Tue, Jul 2, 2024 at 10:36 AM Andrew Morton wrote: > > > > On Tue, 2 Jul 2024 13:21:36 +0000 Yosry Ahmed wrote: > > > > > This series has fixups and cleanups for LAM. Most importantly, patch 1 > > > fixes a sycnhronization issue that may cause crashes of userspace > > > applications. This is a resend of v3, rebased on top of v6.10-rc6. > > > > "Crashes of userspace applications" is bad. Yet the patchset has been > > floating about for four months. > > > > It's unclear (to me) how serious this is. Can you please explain how > > common this is, what the userspace application needs to do to trigger > > this, etc? > > I don't think it would be common. The bug only happens on new hardware > supporting LAM, and it happens in a specific scenario where a > userspace task enables LAM while a kthread is using (borrowing) its > mm_struct on another CPU. > > So it is possible but I certainly wouldn't call it common or easily triggerable. But when people run older (or current) kernels on newer hardware, they will hit this. So a backport to cover 82721d8b25d7 ("x86/mm: Handle LAM on context switch") is needed. The series doesn't seem to be getting much traction so I can add it to mm.git's mm-unstable branch for wider testing, but it's clearly an x86 tree thing.