From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766Ab3KTRZd (ORCPT ); Wed, 20 Nov 2013 12:25:33 -0500 Received: from mga02.intel.com ([134.134.136.20]:1925 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754424Ab3KTRZc (ORCPT ); Wed, 20 Nov 2013 12:25:32 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,535,1378882800"; d="scan'208";a="438650369" From: Andi Kleen To: "H. Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner Subject: Re: [PATCH] Add a text_poke syscall References: <1384820855-27790-1-git-send-email-andi@firstfloor.org> <528AF5D7.7000308@zytor.com> <20131119184959.GE29695@two.firstfloor.org> <528CE65B.6020300@zytor.com> Date: Wed, 20 Nov 2013 09:25:31 -0800 In-Reply-To: <528CE65B.6020300@zytor.com> (H. Peter Anvin's message of "Wed, 20 Nov 2013 08:42:03 -0800") Message-ID: <87mwkzvvck.fsf@tassilo.jf.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "H. Peter Anvin" writes: > > We're talking user space here, which has different requirement (COW, > memory protection, ...) which means it is not really the same code. You > can't take a page fault while patching the kernel. The syscall pins the page, then it calls the kernel code. There are no page faults during patching. > I'm referring to if some thread actually stumbles over INT 3, which is > indeed not very long for one patch site (as long as you don't end up > with page faults.) However, for tracing, you may want to do tens of > thousands of patches, and you really want to batch them. For tens of thousand of patches you very likely don't want live patching, but a stop everything approach. -Andi -- ak@linux.intel.com -- Speaking for myself only