From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Subject: Re: EFI mixed mode + perf = rampant triple faults
Date: Thu, 15 Jan 2015 11:59:42 -0800
Message-ID: <54B81C2E.2090909@zytor.com>
References: <5491B4A8.905@amacapital.net> <CALCETrUyw5_E+FN8o8ZsOxN5XG81-Q8MVzeUHPZ_XBM+ifi6_w@mail.gmail.com> <20141231183739.GA28946@console-pimps.org> <20150114165151.GA3479@codeblueprint.co.uk> <CALCETrWOxPwoL0zo0UZMk=05uAEqgY-Xovk1=JHwbVtinx3u3w@mail.gmail.com> <20150115194127.GB12079@codeblueprint.co.uk>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Return-path: <linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
In-Reply-To: <20150115194127.GB12079-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Matt Fleming <matt-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
Cc: LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
List-Id: linux-efi@vger.kernel.org

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.

	-hpa