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 78727C4332F for ; Mon, 3 Oct 2022 18:51:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C65A18E0001; Mon, 3 Oct 2022 14:51:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BEDEB6B0073; Mon, 3 Oct 2022 14:51:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A3FC88E0001; Mon, 3 Oct 2022 14:51:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8AD5A6B0071 for ; Mon, 3 Oct 2022 14:51:20 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id F2E4CA02AF for ; Mon, 3 Oct 2022 18:51:19 +0000 (UTC) X-FDA: 79980531078.23.1D04E1F Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf14.hostedemail.com (Postfix) with ESMTP id F112110000F for ; Mon, 3 Oct 2022 18:51:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1664823079; x=1696359079; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=sHpGmhITtQ8yrxSaq/GvsC2XRU7DBrZMlLdnk0v7/Vs=; b=XI/vUoYnAnC+xeWRdmS1tTCmAeO/QhYrngZGPLBuUa2Dfm3sxI93rMli IEH+RGT+JGIfpaRanT8653JLnaoYsE8o2V6GIufkeT3vNFq8LuKfwMac9 JSm2awY7vgAvAWYOYQXUss8wmHLhj2X0mJEsweiieL8Z+w/mrFlo0n7gr nY0ITKDf+g7bdLktYOEhWp20nRG1kFae52ojC2ZL9ESR+57jpc46efek4 ZkwutV3HlYUQ+Yf8G9dXv1gqUzKAJkBd9+5TE/t0cu6aakFSbndhkNfy1 Xbwg8ZuC2UqkmDBGT2kQQyersIGvdNC5bBWHEGZ4SGJTWo0Z+RGc20h9v w==; X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="389022208" X-IronPort-AV: E=Sophos;i="5.93,366,1654585200"; d="scan'208";a="389022208" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Oct 2022 11:51:17 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="601347405" X-IronPort-AV: E=Sophos;i="5.93,366,1654585200"; d="scan'208";a="601347405" Received: from akashred-mobl.amr.corp.intel.com (HELO [10.212.139.217]) ([10.212.139.217]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Oct 2022 11:51:16 -0700 Message-ID: <023ee88b-1f23-acb6-9ac6-c75afbcb09d9@intel.com> Date: Mon, 3 Oct 2022 11:51:15 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v2 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Content-Language: en-US To: Nadav Amit , Rick Edgecombe Cc: X86 ML , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , linux-doc@vger.kernel.org, Linux MM , linux-arch , linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V . Shankar" , Weijiang Yang , "Kirill A . Shutemov" , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com, Mike Rapoport , jamorris@linux.microsoft.com, dethoma@microsoft.com, Yu-cheng Yu References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-13-rick.p.edgecombe@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664823079; a=rsa-sha256; cv=none; b=Mt50YuKWVT4q/9bNhnJNMCWNrzmswim+v1vP4NljZUCVcJzcOhM/v/AlGstF8Ty1pScleJ zZd9k1GMWCY/wAJczYclGCxF2PUsktTTGja9g8v5c6IHsC6zyIxpZloUoGk5KRX8/2C7ly m7pybhlxf2lzbgnU5Oq+xo0qncWnX/k= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b="XI/vUoYn"; spf=pass (imf14.hostedemail.com: domain of dave.hansen@intel.com designates 192.55.52.43 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664823079; 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=h73gPAS+N5rhHUWQmUhyMUdSwWwKJxn8XBoWtLjZmJY=; b=k2o14jmg8jLWq7hoQa80rlMnsd/IZ5yR7XqJf557J4ckWg6iajO5InMQDDebeeF42TRuny QsSbV2UX9U932W/m4UKcfY9bQub16CeWM9N6qy9UmGCFzR2XNJpdGCdZP4N9HiPGSkp7/1 wqXfn0iF5bs2wdK2ryn6t/rPKqD5nJE= X-Rspamd-Server: rspam08 X-Rspam-User: X-Rspamd-Queue-Id: F112110000F Authentication-Results: imf14.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b="XI/vUoYn"; spf=pass (imf14.hostedemail.com: domain of dave.hansen@intel.com designates 192.55.52.43 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Stat-Signature: ipuhiipuyq8u9d8xh5xxdirap957ieym X-HE-Tag: 1664823078-634371 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 10/3/22 11:11, Nadav Amit wrote: >> +#ifdef CONFIG_X86_SHADOW_STACK >> + /* >> + * Avoid accidentally creating shadow stack PTEs >> + * (Write=0,Dirty=1). Use cmpxchg() to prevent races with >> + * the hardware setting Dirty=1. >> + */ >> + if (cpu_feature_enabled(X86_FEATURE_SHSTK)) { >> + pte_t old_pte, new_pte; >> + >> + old_pte = READ_ONCE(*ptep); >> + do { >> + new_pte = pte_wrprotect(old_pte); >> + } while (!try_cmpxchg(&ptep->pte, &old_pte.pte, new_pte.pte)); >> + >> + return; >> + } >> +#endif > There is no way of using IS_ENABLED() here instead of these ifdefs? Actually, both the existing #ifdef and an IS_ENABLED() check would be is superfluous as-is. Adding X86_FEATURE_SHSTK disabled-features.h gives cpu_feature_enabled() compile-time optimizations for free. No need for *any* additional CONFIG_* checks. The only issue would be if the #ifdef'd code won't even compile with X86_FEATURE_SHSTK disabled.