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=-2.3 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 CB685C43441 for ; Thu, 22 Nov 2018 20:04:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8414920892 for ; Thu, 22 Nov 2018 20:04:32 +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="diYQAdNo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8414920892 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-security-module-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387455AbeKWGpV (ORCPT ); Fri, 23 Nov 2018 01:45:21 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:50338 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726280AbeKWGpU (ORCPT ); Fri, 23 Nov 2018 01:45:20 -0500 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: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=3iMUh2dkWeYr3Wxskhu4eNYKLzoeaX8kLN4jP9KbV3Y=; b=diYQAdNo0/Z1OVDUdcJUj5cyr kFIDSxC0oD+zPTGgG2cpefx6eEjJueDDF8bO7wAL31DT08IZKtnQSXTeBQiE0S26khoHh8+iLeUU0 tnhLlAdFPNmETrYCM7lM0c5OOdYuv+NqNC4Wp8cj2oNY0b4R+gUZyxL+zgytlZbX13RKtQs0u5R2O tx6TRpwrOeoaT/hJ5gguBahHSBlwQryWsQtuOdOgeW4njwKYevV4rKDrju0cESv4JTKHDMw8OvUF8 6ONLalQU7wN46hsiNcn+98H1iKB+zSYY9sKiM1ySrQXZ2lTOKdOB+w48QC7WnabPA9ITd+Rzk+7WJ e2mXwOvkw==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gPvCy-0007Hx-D4; Thu, 22 Nov 2018 20:04:16 +0000 Date: Thu, 22 Nov 2018 12:04:16 -0800 From: Matthew Wilcox To: Igor Stoppa Cc: Andy Lutomirski , Andy Lutomirski , Igor Stoppa , Nadav Amit , Kees Cook , Peter Zijlstra , Mimi Zohar , Dave Chinner , James Morris , Michal Hocko , Kernel Hardening , linux-integrity , LSM List , 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: <20181122200416.GS3065@bombadil.infradead.org> References: <6f60afc9-0fed-7f95-a11a-9a2eef33094c@gmail.com> <386C0CB1-C4B1-43E2-A754-DA8DBE4FB3CB@gmail.com> <9373ccf0-f51b-4bfa-2b16-e03ebf3c670d@huawei.com> <2e52e103-15d0-0c26-275f-894dfd07e8ec@huawei.com> <1166e55c-0c06-195c-a501-383b4055ea46@gmail.com> <3BB9DE07-E0AE-43E2-99F1-E4AA774CD462@amacapital.net> <5e10c8e4-aa71-1eea-b1ce-50d7d0a60e8c@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e10c8e4-aa71-1eea-b1ce-50d7d0a60e8c@gmail.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Thu, Nov 22, 2018 at 09:27:02PM +0200, Igor Stoppa wrote: > I have studied the code involved with Nadav's patchset. > I am perplexed about these sentences you wrote. > > More to the point (to the best of my understanding): > > poking_init() > ------------- > 1. it gets one random poking address and ensures to have at least 2 > consecutive PTEs from the same PMD > 2. it then proceeds to map/unmap an address from the first of the 2 > consecutive PTEs, so that, later on, there will be no need to > allocate pages, which might fail, if poking from atomic context. > 3. at this point, the page tables are populated, for the address that > was obtained at point 1, and this is ok, because the address is fixed > > write_rare > ---------- > 4. it can happen on any available core / thread at any time, therefore > each of them needs a different address No? Each CPU has its own CR3 (eg each CPU might be running a different user task). If you have _one_ address for each allocation, it may or may not be mapped on other CPUs at the same time -- you simply don't care. The writable address can even be a simple formula to calculate from the read-only address, you don't have to allocate an address in the writable mapping space.