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 D6E57C433EF for ; Wed, 20 Jul 2022 00:59:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5D2066B0072; Tue, 19 Jul 2022 20:59:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5818E6B0073; Tue, 19 Jul 2022 20:59:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 46ECF6B0074; Tue, 19 Jul 2022 20:59:51 -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 399F76B0072 for ; Tue, 19 Jul 2022 20:59:51 -0400 (EDT) Received: from smtpin31.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id D20EE140391 for ; Wed, 20 Jul 2022 00:59:50 +0000 (UTC) X-FDA: 79705670940.31.FDDAA74 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by imf24.hostedemail.com (Postfix) with ESMTP id D7B2918008A for ; Wed, 20 Jul 2022 00:59:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1658278789; x=1689814789; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=nuzHil18hQah8mRqKkYQFzAMHFmMEuGVD8GiUEVxl4A=; b=N/AHqx+v/wcrzSACQ0GnDUnHW4guYgx9o3TDADltWHP03BbVMURpJA/y JDC1D3Mcgfi2/uOLSNh2klunzYkFmNJFexOAqkmHOyovY5TBHDXNKnmIq Oc5vqohUyq7kLz42eKMa/5HS2j6JhqUShdN+wBI8Sa8cYhwhoU2pjTfkt y7p7X8hZoUrJp+QH57LbgZtX8SZyNxPfm8qLk2/63+xjznqP7qCTVMa7d GOuW+M10zL/5qbX6m7mOJzNBHB68GxXUkmRS0Q1sdDo9GFbnr2eLG0Umy Cig3X4If+ZARrKD2krOMgSTmOehZAK4vZ3KmjB1U/qFc2+Lc64jHBC5mt A==; X-IronPort-AV: E=McAfee;i="6400,9594,10413"; a="348340931" X-IronPort-AV: E=Sophos;i="5.92,285,1650956400"; d="scan'208";a="348340931" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Jul 2022 17:59:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,285,1650956400"; d="scan'208";a="687325851" Received: from black.fi.intel.com ([10.237.72.28]) by FMSMGA003.fm.intel.com with ESMTP; 19 Jul 2022 17:59:42 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id C14F9136; Wed, 20 Jul 2022 03:59:50 +0300 (EEST) Date: Wed, 20 Jul 2022 03:59:50 +0300 From: "Kirill A. Shutemov" To: Dave Hansen , Andy Lutomirski , Alexander Potapenko Cc: Peter Zijlstra , the arch/x86 maintainers , Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Taras Madan , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , Linux Memory Management List , LKML Subject: Re: [PATCHv5 00/13] Linear Address Masking enabling Message-ID: <20220720005950.fonulr4kkwbh6kbz@black.fi.intel.com> References: <20220712231328.5294-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b="N/AHqx+v"; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf24.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 134.134.136.31) 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=1658278790; 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=r9JP+DnuRAkVdSzxAJYCsXQqGHPI1JWFFxZVkRsYxWk=; b=E6pZ6/dLp4BNrb7xqHEZ121JwuGTm0XMc/ogcvsNWfosihqXARK0Or0N8PZj6oWTt0Qlmw l+q7q8cyzsExee2tkv//Boeo0/SW1Dl1+HVg3GznFH30p006O5eK2sUC8sYyoXRwUITvW0 NKbaNECtA2u8pS+cc6MF8XhCB2zh6hw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658278790; a=rsa-sha256; cv=none; b=4eypG+ADoJXIeFbDJzDXFhCHo11+DRqDyranKuE/S8PIYcml+FcSjv+81SL1fAIlfpY4Fs vmwIbLLdKGRhl4S3Euq8moH9SJaXRiAAOdJ/Tn040BSKmogqqb/RTUFalpztqjzCNrYIoE CgxKMqQyvXsuBq0sz4WyWNNDlJILBto= X-Stat-Signature: bkc1axcrnrqz57no8r8f9gn6gemihg6y X-Rspamd-Queue-Id: D7B2918008A X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b="N/AHqx+v"; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf24.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 134.134.136.31) smtp.mailfrom=kirill.shutemov@linux.intel.com X-Rspamd-Server: rspam11 X-HE-Tag: 1658278789-299828 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 Mon, Jul 18, 2022 at 07:39:22PM +0200, Alexander Potapenko wrote: > On Wed, Jul 13, 2022 at 1:13 AM Kirill A. Shutemov > wrote: > > > > Linear Address Masking[1] (LAM) modifies the checking that is applied to > > 64-bit linear addresses, allowing software to use of the untranslated > > address bits for metadata. > > > > The patchset brings support for LAM for userspace addresses. > > > > LAM_U48 enabling is controversial since it competes for bits with > > 5-level paging. Its enabling isolated into an optional last patch that > > can be applied at maintainer's discretion. > > I believe having optional patches will put unnecessary burden on > distro maintainers. > Soon after landing U48 support other changes will start piling on top > of it, and it will be impossible to maintain a kernel with this patch > removed. > It also won't make any difference for the upstream, where this patch > will be always present. > > We'd better decide now whether we need U48 or not, and either keep it > or delete it. Dave, Andy, any position on this? I wrote LAM_U48 support to prove that interface is flexible enough, but I see why it can be a problem if a distro will pick them up ahead of upstream. -- Kirill A. Shutemov