From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752645AbaEBViA (ORCPT ); Fri, 2 May 2014 17:38:00 -0400 Received: from mga03.intel.com ([143.182.124.21]:47143 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501AbaEBVh7 (ORCPT ); Fri, 2 May 2014 17:37:59 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,974,1389772800"; d="scan'208";a="426962446" Message-ID: <53641035.4040202@intel.com> Date: Fri, 02 May 2014 14:37:57 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Linus Torvalds , Andy Lutomirski CC: Thomas Gleixner , Linux Kernel Mailing List , the arch/x86 maintainers , Steven Rostedt , Gleb Natapov , Paolo Bonzini Subject: Re: [RFC/HACK] x86: Fast return to kernel References: <210a076ea197ae384705d2c02cfff12a951a62f8.1399057218.git.luto@amacapital.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/02/2014 02:07 PM, Linus Torvalds wrote: > On Fri, May 2, 2014 at 2:04 PM, Andy Lutomirski wrote: >> >> Because otherwise I'd have to keep track of whether it's a zeroentry >> or an errorentry. I can't stuff the offset in a register without even >> more stack hackery, since there are no available registers there. I >> could split the whole thing into two code paths, I guess. > > Ahh. Never mind. I didn't think about the fact that the error entry > case had one more field on the stack. Your approach is all fine, it > was me not seeing the problem. > I have to admit to being rather partial to the idea of simply doing "push $0" on entry for the vectors that don't push an error code, like the early exception handling code does. -hpa