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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8E325C433DF for ; Sun, 24 May 2020 07:42:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 29EE62078B for ; Sun, 24 May 2020 07:42:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="fWl1umd9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 29EE62078B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 979C380008; Sun, 24 May 2020 03:42:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 927BA80007; Sun, 24 May 2020 03:42:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 83DCE80008; Sun, 24 May 2020 03:42:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0125.hostedemail.com [216.40.44.125]) by kanga.kvack.org (Postfix) with ESMTP id 6949080007 for ; Sun, 24 May 2020 03:42:40 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 218D9181AEF00 for ; Sun, 24 May 2020 07:42:40 +0000 (UTC) X-FDA: 76850820480.30.shirt41_1740154f7b756 X-HE-Tag: shirt41_1740154f7b756 X-Filterd-Recvd-Size: 3188 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Sun, 24 May 2020 07:42:39 +0000 (UTC) Received: from kernel.org (unknown [87.71.47.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 26E322076C; Sun, 24 May 2020 07:42:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590306158; bh=+/fFoXXRcAaUgRrF312cHC7kEgpII3DvTDA8eGvdehk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fWl1umd9MDaNFTQL8vtXp9S91lOpXqHQ9cMIrKzvtvJqxr0KCUvLsyHedTsuWhcK+ 8p4N/kJG9k+82H1sIQsHwOKs9c4FXoHV+iXDzQ5Oe5TQpYgYs5FXHs7PZNERJRIt75 vZQkuQA7RKAczl+NpjOLI6H7+2WtBYbABL56OTvw= Date: Sun, 24 May 2020 10:42:30 +0300 From: Mike Rapoport To: Matthew Wilcox Cc: "Kirill A. Shutemov" , 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: <20200524074230.GM1118872@kernel.org> References: <20200428194449.22615-1-willy@infradead.org> <20200429002624.qkhb362moj6v3vtw@box> <20200429015126.GP29705@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200429015126.GP29705@bombadil.infradead.org> 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 Tue, Apr 28, 2020 at 06:51:26PM -0700, Matthew Wilcox wrote: > 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 A note to keep in mind is that most of the kernel page tables are seen as PG_reserved rather than PageTable(). > > 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. > -- Sincerely yours, Mike.