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 1D67AC433FE for ; Mon, 3 Oct 2022 18:03:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A7DD76B0071; Mon, 3 Oct 2022 14:03:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A2D2A8E0002; Mon, 3 Oct 2022 14:03:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F5328E0001; Mon, 3 Oct 2022 14:03:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 7DD526B0071 for ; Mon, 3 Oct 2022 14:03:10 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 53E94C0AD0 for ; Mon, 3 Oct 2022 18:03:10 +0000 (UTC) X-FDA: 79980409740.14.183C900 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf26.hostedemail.com (Postfix) with ESMTP id 52DA0140024 for ; Mon, 3 Oct 2022 18:03:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1664820189; x=1696356189; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=cjgd5Rwu0UYo06yOUVIVHZGW70aBVle99QVapUa4l8I=; b=Fgk5SDHlQZzQnFtBNnbYjXb2XWzHc8SBSPtBrSPszk390ClnYUvVQMHH lXZ2+/5aDOYsAJLD0edLntko1uBq7oLDgvktAEdysZzNUTnsQmZrL3YN6 pXtCmlp2dDapJr+YacyE7vaFZa+ZBiMv9y34luRz8GVUIx9clJARdTdS9 QEbgGdAmwOVC8Fq8VXcQiisXY/xsp9HnwVy80VCVFIdv5ceFJB5IWu5Kf CUtXuQrFeTRA79dfS1V18r/MoOkBj/upPmP2uvCvQ6/zRAyOBeG7bASPr 6/EmB6Ixrh03ym+uSt+ZuEVGOSz46YjjJYeD/Xw0ZHUaohTCxv0lW5nFQ A==; X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="303654653" X-IronPort-AV: E=Sophos;i="5.93,366,1654585200"; d="scan'208";a="303654653" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Oct 2022 10:43:55 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="574724070" X-IronPort-AV: E=Sophos;i="5.93,366,1654585200"; d="scan'208";a="574724070" Received: from bandrei-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.252.37.219]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Oct 2022 10:43:45 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id D42D2104CE4; Mon, 3 Oct 2022 20:43:41 +0300 (+03) Date: Mon, 3 Oct 2022 20:43:41 +0300 From: "Kirill A . Shutemov" To: Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, 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 , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V . Shankar" , Weijiang Yang , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, Yu-cheng Yu Subject: Re: [PATCH v2 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Message-ID: <20221003174341.oqpypr4lsdrfga7f@box.shutemov.name> References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-13-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220929222936.14584-13-rick.p.edgecombe@intel.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664820189; 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=aFitenwiENytUBZ8dtve/+Ahn7wDnjFRSwsdnPnBosE=; b=KpkDeurnLaWKFcuckcRgvJYmUwTRTbge6+sw62d3D29rCJW+iIPZD9dS1u6pT74UxpmEWF fi1F4sTNb3iPSqWfbjERsHxODz5ulqRD7Iu6p4Qi9dNc0whNzs3pltr2PPEg4ke/qr6nTI iQGO+PBzV2+dXE2yJoAyOZWnZ/Vw5dE= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=Fgk5SDHl; spf=none (imf26.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 134.134.136.24) smtp.mailfrom=kirill.shutemov@linux.intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664820190; a=rsa-sha256; cv=none; b=NMpIRWLU5v0/lOsdN9JPlbW9TqqxUq2DZcqdw5xD5aiyfn0O4E5fbGCkXX/claX53YBVgJ iKuFsc8DQpFE//Z3spHW6Mh87D+DI7MRqUDnQLA2THU83f5U/sgmEwXXenXUvL2dFXwi3J pindHM1NJ5k9MCgThdCZtroa94tNLA0= X-Rspamd-Queue-Id: 52DA0140024 Authentication-Results: imf26.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=Fgk5SDHl; spf=none (imf26.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 134.134.136.24) smtp.mailfrom=kirill.shutemov@linux.intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) X-Rspamd-Server: rspam06 X-Rspam-User: X-Stat-Signature: 4f19gp7456ce31xe8wbdxnj8sek576dj X-HE-Tag: 1664820188-760407 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 Thu, Sep 29, 2022 at 03:29:09PM -0700, Rick Edgecombe wrote: > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 2f2963429f48..58c7bf9d7392 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -1287,6 +1287,23 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, > static inline void ptep_set_wrprotect(struct mm_struct *mm, > unsigned long addr, pte_t *ptep) > { > +#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 > clear_bit(_PAGE_BIT_RW, (unsigned long *)&ptep->pte); > } Okay, this addresses my previous question. The need in cmpxchg is unfortunate, but well. -- Kiryl Shutsemau / Kirill A. Shutemov