From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932370AbbAOWVI (ORCPT ); Thu, 15 Jan 2015 17:21:08 -0500 Received: from mail-wi0-f181.google.com ([209.85.212.181]:43169 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755567AbbAOWVF (ORCPT ); Thu, 15 Jan 2015 17:21:05 -0500 Date: Thu, 15 Jan 2015 22:21:01 +0000 From: Matt Fleming To: "H. Peter Anvin" Cc: Andy Lutomirski , LKML , "linux-efi@vger.kernel.org" , Borislav Petkov , Thomas Gleixner , Ingo Molnar , Peter Zijlstra Subject: Re: EFI mixed mode + perf = rampant triple faults Message-ID: <20150115222101.GE12079@codeblueprint.co.uk> References: <5491B4A8.905@amacapital.net> <20141231183739.GA28946@console-pimps.org> <20150114165151.GA3479@codeblueprint.co.uk> <20150115194127.GB12079@codeblueprint.co.uk> <54B81C2E.2090909@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54B81C2E.2090909@zytor.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 15 Jan, at 11:59:42AM, H. Peter Anvin wrote: > On 01/15/2015 11:41 AM, Matt Fleming wrote: > >> > >>Tianocore makes assumptions about the kernel's GDT layout? Yuck. > > > >No, but 32-bit Tianocore does rely on the second GDT entry being a > >32-bit CS. > > > >It has no knowledge of Linux's GDT layout. > > > > If it assumes that descriptor 16 is a 32-bit CS (and what about > data? 24?) that *is* making assumptions on the kernel. Bear in mind that this is before ExitBootServices() is invoked, so where the firmware still thinks it (not the OS) "owns" the platform. None of this comes into play at Runtime. -- Matt Fleming, Intel Open Source Technology Center