From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752961AbaEBUHf (ORCPT ); Fri, 2 May 2014 16:07:35 -0400 Received: from mga03.intel.com ([143.182.124.21]:51041 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbaEBUHe (ORCPT ); Fri, 2 May 2014 16:07:34 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,974,1389772800"; d="scan'208";a="426935221" Message-ID: <5363FB05.4000302@intel.com> Date: Fri, 02 May 2014 13:07:33 -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: 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 12:51 PM, Linus Torvalds wrote: > On Fri, May 2, 2014 at 12:31 PM, Linus Torvalds > wrote: >> >> Also, are you *really* sure that "popf" has the same one-instruction >> interrupt shadow that "sti" has? Because I'm not at all sure that is >> true, and it's not documented as far as I can tell. In contrast, the >> one-instruction shadow after "sti" very much _is_ documented. > > Yeah, I'm pretty sure about this. The only instructions with an > interrupt shadow are "sti", "mov ss" and "pop ss". > I believe you are correct here. -hpa