From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f72.google.com (mail-it0-f72.google.com [209.85.214.72]) by kanga.kvack.org (Postfix) with ESMTP id A1E6D6B025F for ; Tue, 29 Aug 2017 17:20:36 -0400 (EDT) Received: by mail-it0-f72.google.com with SMTP id p2so5947618ite.9 for ; Tue, 29 Aug 2017 14:20:36 -0700 (PDT) Received: from gate.crashing.org (gate.crashing.org. [63.228.1.57]) by mx.google.com with ESMTPS id w64si3802821ioe.160.2017.08.29.14.20.35 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 29 Aug 2017 14:20:35 -0700 (PDT) Message-ID: <1504041570.2358.30.camel@kernel.crashing.org> Subject: Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure From: Benjamin Herrenschmidt Date: Wed, 30 Aug 2017 07:19:30 +1000 In-Reply-To: <20170829112731.vhgwrzwwlimdbjcn@hirez.programming.kicks-ass.net> References: <1503007519-26777-1-git-send-email-ldufour@linux.vnet.ibm.com> <1503007519-26777-15-git-send-email-ldufour@linux.vnet.ibm.com> <20170827001823.n5wgkfq36z6snvf2@node.shutemov.name> <20170828093727.5wldedputadanssh@hirez.programming.kicks-ass.net> <1503954877.4850.19.camel@kernel.crashing.org> <20170829083352.qrsxvk3lkiydi3o2@hirez.programming.kicks-ass.net> <20170829112731.vhgwrzwwlimdbjcn@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: "Kirill A. Shutemov" , Laurent Dufour , paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org On Tue, 2017-08-29 at 13:27 +0200, Peter Zijlstra wrote: > mpe helped me out and explained that is the PWC hint to TBLIE. > > So, you set need_flush_all when you unhook pud/pmd/pte which you then > use to set PWC. So free_pgtables() will do the PWC when it unhooks > higher level pages. > > But you're right that there's some issues, free_pgtables() itself > doesn't seem to use mm->page_table_lock,pmd->lock _AT_ALL_ to unhook the > pages. > > If it were to do that, things should work fine since those locks would > then serialize against the speculative faults, we would never install a > page if the VMA would be under tear-down and it would thus not be > visible to your caches either. That's one case. I don't remember of *all* the cases to be honest, but I do remember several times over the past few years thinking "ah we are fine because the mm sem taken for writing protects us from any concurrent tree structure change" :-) Cheers, Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org