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 04275C433EF for ; Tue, 28 Jun 2022 23:42:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 905A06B0071; Tue, 28 Jun 2022 19:42:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8B5496B0072; Tue, 28 Jun 2022 19:42:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7CBB98E0001; Tue, 28 Jun 2022 19:42:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 6DBF46B0071 for ; Tue, 28 Jun 2022 19:42:44 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 22569534 for ; Tue, 28 Jun 2022 23:42:44 +0000 (UTC) X-FDA: 79629271848.29.A906815 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf15.hostedemail.com (Postfix) with ESMTP id BC106A000E for ; Tue, 28 Jun 2022 23:42:43 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E441761B75; Tue, 28 Jun 2022 23:42:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AA4DC341C8; Tue, 28 Jun 2022 23:42:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656459762; bh=ZXEgiKdFj904q2Qs5SYcsF0x6Q/LuLJtPywfGr8yB4A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=RYAZHRn3GAgv5+2JiJAS7wrZ1C9zj0e37sYid++Tw9kVuQCwhYrNUwH7zCe438tBt CVYNZi+xk8ufEsoRiCHlINgk/TG1NQj7GFhHJQGs+5KglAcXilUI4MzTsDp6DgxYh5 MK828g1PI6UeLpwlWOSsc5lXWDi3g0auxOn7VitPF5LZMCX4wjTFQqbS8UfzpJtxdx OKP7L+qaSC/7d5w1dhvETH+ydpbsEIANJtyb8ERs8ALRGqseMbNq0dmNYwUpu4uX66 3QKhSup2q31+bA5JSJ07TCf4EZit8mq0g6ZBv/ckKYnQNpMjLzMHAEy4gqZijEMNFI P/HXF8LfTYB/g== Message-ID: <6cb17661-9436-afbf-38eb-58565bba1a56@kernel.org> Date: Tue, 28 Jun 2022 16:42:40 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR Content-Language: en-US To: "Kirill A. Shutemov" , Dave Hansen , Peter Zijlstra Cc: x86@kernel.org, Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220610143527.22974-1-kirill.shutemov@linux.intel.com> <20220610143527.22974-7-kirill.shutemov@linux.intel.com> From: Andy Lutomirski In-Reply-To: <20220610143527.22974-7-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656459763; a=rsa-sha256; cv=none; b=RyzgK/4bCHWldmFHVf6tSCcN/3PJlpuKHZ6a+Q0o7AgCbPZQpW/1ovC78qH98kbYJa/nmg xV3Akn2oz547pIGcsceDNjYuU7DhjC3sdjXMY3RiNK29StMTmEwbvZKdOeq5VVv5NwWCZT DRY1DSeTxPONpRFVGsWEXhTwwLP6mhM= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=RYAZHRn3; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf15.hostedemail.com: domain of luto@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=luto@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656459763; 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=fy2YWGHDvWy76yipnMFJbzAyJoiiVW4e8hhUOAKoQck=; b=VS/SZtaaHU7TeYFCffByWhVVGaWwmBxz0Tt9ASuRxBTBZ6IN4IJaIkOTdDs/UrcIwVxkPU v+tzdz+38qtJrXyfdkr9yXOZeHpqkBcDxNwdtSlREwba+sJQPudlke2OHztzfC+CQJxvix YSlzDH1h+1r7l029FuyJWkGpDHhejaU= X-Stat-Signature: x83aztoy5bf5k9g5zbi7wkm5odzwypqd X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BC106A000E Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=RYAZHRn3; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf15.hostedemail.com: domain of luto@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=luto@kernel.org X-HE-Tag: 1656459763-736293 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 6/10/22 07:35, Kirill A. Shutemov wrote: > + /* Update CR3 to get LAM active */ > + switch_mm(current->mm, current->mm, current); Can you at least justify this oddity? When changing an LDT, we use a dedicated mechanism. Is there a significant benefit to abusing switch_mm for this? Also, why can't we enable LAM on a multithreaded process? We can change an LDT, and the code isn't even particularly complicated.