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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28EF0C5CFE7 for ; Wed, 11 Jul 2018 16:14:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF7ED20C0C for ; Wed, 11 Jul 2018 16:14:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF7ED20C0C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387781AbeGKQTv (ORCPT ); Wed, 11 Jul 2018 12:19:51 -0400 Received: from mga03.intel.com ([134.134.136.65]:16374 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726457AbeGKQTv (ORCPT ); Wed, 11 Jul 2018 12:19:51 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Jul 2018 09:14:42 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,338,1526367600"; d="scan'208";a="70522785" Received: from 2b52.sc.intel.com ([143.183.136.52]) by fmsmga004.fm.intel.com with ESMTP; 11 Jul 2018 09:14:40 -0700 Message-ID: <1531325463.13297.30.camel@intel.com> Subject: Re: [RFC PATCH v2 14/27] mm: Handle THP/HugeTLB shadow stack page fault From: Yu-cheng Yu To: Peter Zijlstra 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 , Cyrill Gorcunov , Dave Hansen , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , "Ravi V. Shankar" , Vedvyas Shanbhogue Date: Wed, 11 Jul 2018 09:11:03 -0700 In-Reply-To: <20180711091022.GT2476@hirez.programming.kicks-ass.net> References: <20180710222639.8241-1-yu-cheng.yu@intel.com> <20180710222639.8241-15-yu-cheng.yu@intel.com> <20180711091022.GT2476@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2018-07-11 at 11:10 +0200, Peter Zijlstra wrote: > On Tue, Jul 10, 2018 at 03:26:26PM -0700, Yu-cheng Yu wrote: > > > > diff --git a/mm/memory.c b/mm/memory.c > > index a2695dbc0418..f7c46d61eaea 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -4108,7 +4108,13 @@ static int __handle_mm_fault(struct > > vm_area_struct *vma, unsigned long address, > >   if (pmd_protnone(orig_pmd) && > > vma_is_accessible(vma)) > >   return do_huge_pmd_numa_page(&vmf, > > orig_pmd); > >   > > - if (dirty && !pmd_write(orig_pmd)) { > > + /* > > +  * Shadow stack trans huge PMDs are copy- > > on-access, > > +  * so wp_huge_pmd() on them no mater if we > > have a > > +  * write fault or not. > > +  */ > > + if (is_shstk_mapping(vma->vm_flags) || > > +     (dirty && !pmd_write(orig_pmd))) { > >   ret = wp_huge_pmd(&vmf, orig_pmd); > >   if (!(ret & VM_FAULT_FALLBACK)) > >   return ret; > Can't we do this (and the do_wp_page thing) by setting > FAULT_FLAG_WRITE > in the arch fault handler on shadow stack faults? This can work.  I don't know if that will create other issues. Let me think about that. Yu-cheng