From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755788AbZKCE5X (ORCPT ); Mon, 2 Nov 2009 23:57:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755539AbZKCE5X (ORCPT ); Mon, 2 Nov 2009 23:57:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:30662 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755460AbZKCE5W (ORCPT ); Mon, 2 Nov 2009 23:57:22 -0500 Message-ID: <4AEFB823.4040607@redhat.com> Date: Tue, 03 Nov 2009 06:57:07 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-3.9.b4.fc12 Thunderbird/3.0b4 MIME-Version: 1.0 To: Rik van Riel CC: Ingo Molnar , Gleb Natapov , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "H. Peter Anvin" , Thomas Gleixner Subject: Re: [PATCH 02/11] Add "handle page fault" PV helper. References: <1257076590-29559-1-git-send-email-gleb@redhat.com> <1257076590-29559-3-git-send-email-gleb@redhat.com> <20091102092214.GB8933@elte.hu> <4AEF2D0A.4070807@redhat.com> <4AEF3419.1050200@redhat.com> <4AEF6CC3.4000508@redhat.com> In-Reply-To: <4AEF6CC3.4000508@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/03/2009 01:35 AM, Rik van Riel wrote: >> We can't add an exception vector since all the existing ones are either >> taken or reserved. > > > I believe some are reserved for operating system use. Table 6-1 says: 9 | | Coprocessor Segment Overrun (reserved) | Fault | No | Floating-point instruction.2 15 | — | (Intel reserved. Do not use.) | | No | 20-31 | — | Intel reserved. Do not use. | 32-255 | — | User Defined (Non-reserved) Interrupts | Interrupt | | External interrupt or INT n instruction. So we can only use 32-255, but these are not fault-like exceptions that can be delivered with interrupts disabled. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.