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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 B0E9EECDE46 for ; Wed, 31 Oct 2018 10:11:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74DF720685 for ; Wed, 31 Oct 2018 10:11:59 +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="XE6cCwPx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74DF720685 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1728346AbeJaTJ0 (ORCPT ); Wed, 31 Oct 2018 15:09:26 -0400 Received: from merlin.infradead.org ([205.233.59.134]:35630 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727692AbeJaTJ0 (ORCPT ); Wed, 31 Oct 2018 15:09:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=gq+In4AB5xCINJI4HV1K716XlMaT2LdiwoPTCQL+wv4=; b=XE6cCwPxeHBHyBSmrkkSTtRE4 fFj0439HWdMorMVwv7jsOrdkAXPvSjMnG/TENzReeveGoTBa+dxhZ76iqkmyThYV/MB1dmgIPVqQD MSKW5vE1nLpkVp6eBNJowgXIICZK7MbBSZUKahue+7DkfjGMRbFJvFyPf99SqB95s3MrWytVaO4jf 51lu/xx4Qn4ZxcZbAUCoYETUTMyP21EfRyu9SmJn9YN/f42JOr7Bk1P1enkB2Pkn/e4MoXiAxENhO G87ck59YrOaR4fQ2/VojZzeVciQeAaKM9RVVxbQqXVNCiE30fW+THRoTmxgxZNEZ2lKjn3j4mg7Cj Eoe6im17Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gHnTD-0002jN-Qt; Wed, 31 Oct 2018 10:11:28 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 34E802029FA14; Wed, 31 Oct 2018 11:11:24 +0100 (CET) Date: Wed, 31 Oct 2018 11:11:24 +0100 From: Peter Zijlstra To: Igor Stoppa Cc: Andy Lutomirski , Matthew Wilcox , Tycho Andersen , Kees Cook , Mimi Zohar , Dave Chinner , James Morris , Michal Hocko , Kernel Hardening , linux-integrity , linux-security-module , Igor Stoppa , Dave Hansen , Jonathan Corbet , Laura Abbott , Randy Dunlap , Mike Rapoport , "open list:DOCUMENTATION" , LKML , Thomas Gleixner Subject: Re: [PATCH 10/17] prmem: documentation Message-ID: <20181031101124.GO744@hirez.programming.kicks-ass.net> References: <40cd77ce-f234-3213-f3cb-0c3137c5e201@gmail.com> <20181030152641.GE8177@hirez.programming.kicks-ass.net> <0A7AFB50-9ADE-4E12-B541-EC7839223B65@amacapital.net> <20181030175814.GB10491@bombadil.infradead.org> <20181030182841.GE7343@cisco> <20181030192021.GC10491@bombadil.infradead.org> <9edbdf8b-b5fb-5a82-43b4-b639f5ec8484@gmail.com> <2cfb3835-0c18-b3fb-1722-5d693ae0ecd2@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2cfb3835-0c18-b3fb-1722-5d693ae0ecd2@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 31, 2018 at 12:15:46AM +0200, Igor Stoppa wrote: > On 30/10/2018 23:02, Andy Lutomirski wrote: > > But I dislike allowing regular writes in the protected region. We > > really only need four write primitives: > > > > 1. Just write one value. Call at any time (except NMI). > > > > 2. Just copy some bytes. Same as (1) but any number of bytes. > > > > 3,4: Same as 1 and 2 but must be called inside a special rare write > > region. This is purely an optimization. > > Atomic? RCU? RCU can be done, that's not really a problem. Atomics otoh are a problem. Having pointers makes them just work. Andy; I understand your reason for not wanting them, but I really don't want to duplicate everything. Is there something we can do with static analysis to make you more comfortable with the pointer thing?