From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754802Ab3KTSb3 (ORCPT ); Wed, 20 Nov 2013 13:31:29 -0500 Received: from terminus.zytor.com ([198.137.202.10]:39277 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373Ab3KTSb2 (ORCPT ); Wed, 20 Nov 2013 13:31:28 -0500 User-Agent: K-9 Mail for Android In-Reply-To: <87mwkzvvck.fsf@tassilo.jf.intel.com> References: <1384820855-27790-1-git-send-email-andi@firstfloor.org> <528AF5D7.7000308@zytor.com> <20131119184959.GE29695@two.firstfloor.org> <528CE65B.6020300@zytor.com> <87mwkzvvck.fsf@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [PATCH] Add a text_poke syscall From: "H. Peter Anvin" Date: Wed, 20 Nov 2013 10:30:56 -0800 To: Andi Kleen CC: x86@kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner Message-ID: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Why? Live patching works fine and keys the other threads run along just fine. We do this for ftrace already... Andi Kleen wrote: >"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 -- Sent from my mobile phone. Please pardon brevity and lack of formatting.