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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 1180EC83006 for ; Wed, 29 Apr 2020 01:51:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE16E2073E for ; Wed, 29 Apr 2020 01:51:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Ul2ClHCm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726426AbgD2Bva (ORCPT ); Tue, 28 Apr 2020 21:51:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726158AbgD2Bva (ORCPT ); Tue, 28 Apr 2020 21:51:30 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F324C03C1AC; Tue, 28 Apr 2020 18:51:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=WbbJxxgU3/2bFydTDSvswBZ7GGGONTFQzERhB4EnAUc=; b=Ul2ClHCmMLDUyloGhXGz54hFzD fMR+V0dNgvkNCYvShBkoTv6vBoaB8q70JyqyVLyqXTRrRx8yre3Sj8KAOfTYayVF+xLVzJwcsYB0s hjurit9iWN4a5sfT/dChjGHZuP5ERi+QmDTiiNv0kCZTz8PZM16OX32LiQsN4Em+etdl3Yrc30Yxw g/FLckZ/pLl7ZUy6rZCNq18s1PAAYOaxZB8Pr4KVT3AKuNvF9uNXhTJRGRiSx6zGLAYTsDr4gk9N0 skWVoLsycEX4MKtlyewMifsVXMO+sT7X1qmpJQJKOt9VDpJ2AVrLCslMj+PaSe2mIz9EdWa+BzpBC gssJLDhA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTbsk-000812-Hw; Wed, 29 Apr 2020 01:51:26 +0000 Date: Tue, 28 Apr 2020 18:51:26 -0700 From: Matthew Wilcox To: "Kirill A. Shutemov" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Will Deacon , Catalin Marinas , Russell King , Geert Uytterhoeven , linux-m68k@lists.linux-m68k.org Subject: Re: [PATCH 0/7] Record the mm_struct in the page table pages Message-ID: <20200429015126.GP29705@bombadil.infradead.org> References: <20200428194449.22615-1-willy@infradead.org> <20200429002624.qkhb362moj6v3vtw@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200429002624.qkhb362moj6v3vtw@box> Sender: linux-m68k-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org On Wed, Apr 29, 2020 at 03:26:24AM +0300, Kirill A. Shutemov wrote: > On Tue, Apr 28, 2020 at 12:44:42PM -0700, Matthew Wilcox wrote: > > From: "Matthew Wilcox (Oracle)" > > > > Pages which are in use as page tables have some space unused in struct > > page. It would be handy to have a pointer to the struct mm_struct that > > they belong to so that we can handle uncorrectable errors in page tables > > more gracefully. There are a few other things we could use it for too, > > such as checking that the page table entry actually belongs to the task > > we think it ought to. This patch series does none of that, but does > > lay the groundwork for it. > > > > Matthew Wilcox (Oracle) (7): > > How does it work for kernel side of virtual address space? init_mm > And your employer may be interested in semantics around > CONFIG_ARCH_WANT_HUGE_PMD_SHARE :P I was thinking about that. Right now, it's only useful for debugging purposes (as you point out in a later email). I think it's OK if shared PMDs aren't supported as well as regular PTEs, just because there are so few of them that uncorrectable errors are less likely to strike in those pages.