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 F3BFBC433EF for ; Fri, 10 Jun 2022 18:06:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 756EE8D00D5; Fri, 10 Jun 2022 14:06:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6B8DF8D00CB; Fri, 10 Jun 2022 14:06:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 50B918D00D5; Fri, 10 Jun 2022 14:06:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 3D2C78D00CB for ; Fri, 10 Jun 2022 14:06:41 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 143BF815FE for ; Fri, 10 Jun 2022 18:06:41 +0000 (UTC) X-FDA: 79563106602.13.8675C58 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by imf27.hostedemail.com (Postfix) with ESMTP id F40A94007C for ; Fri, 10 Jun 2022 18:06:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1654884400; x=1686420400; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=IFRrzvN2oP18xaw+PepMuRmspRZRLwDxgXN4BczW7yk=; b=mLSIaCggrpKNI5Q7LA1yh1lm10cKK6Y5mXMqHAzB0pq68i8eqysZIH1u 9ehqbhr2+fpnC2vv4Pfp3OWA7KGl3N4gbv5Dk+8W+/rpy+Q05Vc7dexQO dz1OSDdG6Hu+Lz5/LC95t8Du6IzuX/X6txuJZi6nKOAochAWoBVGOU+xf Iu9tCxkqEYocF0TqjWXY3FqD7khq8ixdN++1fqGQ5OvnYJ80c/54JRGaa StTz7WcinjBgtkZPAvR8GCi3j3aAs/Fs4KIazozSpq8rJ7NoBLSb3g5pi XYRlW0lji3GlIKWXUqsR5NO0opgOBowGbfMTi5aPmNgU74sFsSCJiJ5DK Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10374"; a="276481960" X-IronPort-AV: E=Sophos;i="5.91,291,1647327600"; d="scan'208";a="276481960" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jun 2022 11:06:36 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.91,291,1647327600"; d="scan'208";a="760612596" Received: from black.fi.intel.com ([10.237.72.28]) by orsmga005.jf.intel.com with ESMTP; 10 Jun 2022 11:06:32 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id B4787F8; Fri, 10 Jun 2022 21:06:35 +0300 (EEST) Date: Fri, 10 Jun 2022 21:06:35 +0300 From: "Kirill A. Shutemov" To: "Edgecombe, Rick P" Cc: "peterz@infradead.org" , "Lutomirski, Andy" , "dave.hansen@linux.intel.com" , "linux-kernel@vger.kernel.org" , "hjl.tools@gmail.com" , "linux-mm@kvack.org" , "kcc@google.com" , "andreyknvl@gmail.com" , "ak@linux.intel.com" , "dvyukov@google.com" , "x86@kernel.org" , "ryabinin.a.a@gmail.com" , "glider@google.com" Subject: Re: [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR Message-ID: <20220610180635.l44opq2votd3gxpl@black.fi.intel.com> References: <20220610143527.22974-1-kirill.shutemov@linux.intel.com> <20220610143527.22974-7-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1654884400; a=rsa-sha256; cv=none; b=tqUDjY/jgLecefGK8kzmS5RsbhoelstYP70JOs5maiF13WgpG9dA3cdmEDMBItaUJXdrs3 CgelQMRs2rs++2ZKCb4wib/tV0MXv2hi+qUc2vgze54ju6FBVvQcfYLRYGt7ixhfWJORLD 8TPfe3/xuMrMBjjSh+wwX5eNNY/T7b4= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=mLSIaCgg; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf27.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 192.55.52.120) smtp.mailfrom=kirill.shutemov@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1654884400; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=vHNSBQB4b9Jnw6OILZ1ECDuBu1szXs9nggOqV9wtEaA=; b=sFs5YA9CECsvd6H/hKcGwyNHrb3UqGgZIjn9y0o/aCBX089hKWrc4KgLI5RzwdKavVWm88 A9sWb90VO8eh4GfPyTz0RFfmfcA9iaTJL6NQ7fMVrvF7CqVY+OK2s5X5KJw/XyM9Ym2euF v0Ud656DDwnImd2F51oweyqgfdQEprU= X-Rspamd-Queue-Id: F40A94007C X-Rspam-User: Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=mLSIaCgg; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf27.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 192.55.52.120) smtp.mailfrom=kirill.shutemov@linux.intel.com X-Stat-Signature: degme3w7fregjm4gdn7sffr1nytou4eb X-Rspamd-Server: rspam02 X-HE-Tag: 1654884399-336343 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 Fri, Jun 10, 2022 at 04:16:01PM +0000, Edgecombe, Rick P wrote: > On Fri, 2022-06-10 at 17:35 +0300, Kirill A. Shutemov wrote: > > +static int prctl_enable_tagged_addr(unsigned long nr_bits) > > +{ > > + struct mm_struct *mm = current->mm; > > + > > + /* Already enabled? */ > > + if (mm->context.lam_cr3_mask) > > + return -EBUSY; > > + > > + /* LAM has to be enabled before spawning threads */ > > + if (get_nr_threads(current) > 1) > > + return -EBUSY; > > Does this work for vfork()? I guess the idea is that locking is not > needed below because there is only one thread with the MM, but with > vfork() another task could operate on the MM, call fork(), etc. I'm not > sure... I'm not sure I follow. vfork() blocks parent process until child exit or execve(). I don't see how it is a problem. -- Kirill A. Shutemov