From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753258AbdKVWyf (ORCPT ); Wed, 22 Nov 2017 17:54:35 -0500 Received: from mga06.intel.com ([134.134.136.31]:9946 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752194AbdKVWyd (ORCPT ); Wed, 22 Nov 2017 17:54:33 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,438,1505804400"; d="scan'208";a="152262833" Subject: Re: [PATCH 08/30] x86, kaiser: unmap kernel from userspace page tables (core patch) To: Thomas Gleixner References: <20171110193058.BECA7D88@viggo.jf.intel.com> <20171110193112.6A962D6A@viggo.jf.intel.com> Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, richard.fellner@student.tugraz.at, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, x86@kernel.org From: Dave Hansen Message-ID: <63daa6c0-76de-ee67-6a77-fef601a22943@linux.intel.com> Date: Wed, 22 Nov 2017 14:54:29 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/20/2017 09:21 AM, Thomas Gleixner wrote: >> +page tables are switched to the full "kernel" copy. When the >> +system switches back to user mode, the user/shadow copy is used. >> + >> +The minimalistic kernel portion of the user page tables try to >> +map only what is needed to enter/exit the kernel such as the >> +entry/exit functions themselves and the interrupt descriptor >> +table (IDT). > s/try to// Actually, they do _aspire_ "to map only what is needed". But, there *is* some non-necessary cruft (like the first C function in an interrupt). So, removing this language actually makes the description less precise.