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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 51EF4C3A59E for ; Thu, 5 Sep 2019 01:49:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1BEC220882 for ; Thu, 5 Sep 2019 01:49:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567648185; bh=zo9ULV+hpAXsuDOpSM2OjIMnQQSkYg7lHRWUmgT2DiI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=y2uA2A0DsqrFqYs5wPAkXhlyFEYudoQnztsnaJq1bhX/waxZH0OziDmKRl4XZrLks l6z+1NXcqR6YPKXmoYQRx2n5t3Rf/HfzRot60bzPjZYnDkwwvg+dsP4FVPM5uVParU BxpgvqCZlDdisX7We5iQgyYB+teecCN9/zLJhxN0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730628AbfIEBto (ORCPT ); Wed, 4 Sep 2019 21:49:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:34182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727156AbfIEBto (ORCPT ); Wed, 4 Sep 2019 21:49:44 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4EB0B20644; Thu, 5 Sep 2019 01:49:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567648183; bh=zo9ULV+hpAXsuDOpSM2OjIMnQQSkYg7lHRWUmgT2DiI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Spbz7M6vwU7hElCNqtXo3bKV+4/MX5UPtIN8l2p64GEiBqZISlxfa5bc1OunLPkii bjeBNfoO6cFJ+tXKjrc3gwOfSyZt/cOnKZ4x/xtyWeGsP5iif9c19VeSAr71jIuM6U DBVkcDC04fNdgCH4YhXG55EE5a7IGmP7Qh4b0Q98= Date: Thu, 5 Sep 2019 10:49:37 +0900 From: Masami Hiramatsu To: Andrew Cooper Cc: Ingo Molnar , Juergen Gross , Stefano Stabellini , Peter Zijlstra , Randy Dunlap , , , Borislav Petkov , Josh Poimboeuf , , Boris Ostrovsky Subject: Re: [Xen-devel] [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX Message-Id: <20190905104937.60aa03f699a9c0fbf1b651b9@kernel.org> In-Reply-To: References: <156759754770.24473.11832897710080799131.stgit@devnote2> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 4 Sep 2019 12:54:55 +0100 Andrew Cooper wrote: > On 04/09/2019 12:45, Masami Hiramatsu wrote: > > Hi, > > > > These patches allow x86 instruction decoder to decode > > xen-cpuid which has XEN_EMULATE_PREFIX, and prohibit > > kprobes to probe on it. > > > > Josh reported that the objtool can not decode such special > > prefixed instructions, and I found that we also have to > > prohibit kprobes to probe on such instruction. > > > > This series can be applied on -tip master branch which > > has merged Josh's objtool/perf sharing common x86 insn > > decoder series. > > The paravirtualised xen-cpuid is were you'll see it most in a regular > kernel, but be aware that it is also used for testing purposes in other > circumstances, and there is an equivalent KVM prefix which is used for > KVM testing. Good catch! I didn't notice that. Is that really same sequance or KVM uses another sequence of instructions for KVM prefix? > > It might be better to generalise the decode support to "virtualisation > escape prefix" or something slightly more generic. Agreed, it is easy to expand it, we can switch the prefix template. Could you tell me where I should look? I will add it. Thank you, > > ~Andrew -- Masami Hiramatsu