From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752348Ab3ITP3J (ORCPT ); Fri, 20 Sep 2013 11:29:09 -0400 Received: from arkanian.console-pimps.org ([212.110.184.194]:49817 "EHLO arkanian.console-pimps.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751737Ab3ITP3H (ORCPT ); Fri, 20 Sep 2013 11:29:07 -0400 Date: Fri, 20 Sep 2013 16:28:59 +0100 From: Matt Fleming To: Bart Kuivenhoven Cc: matt.fleming@intel.com, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, jcm@redhat.com, msalter@redhat.com Subject: Re: [PATCH] x86 efi: bugfix interrupt disabling sequence Message-ID: <20130920152859.GC21381@console-pimps.org> References: <1379525333-4373-1-git-send-email-bemk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1379525333-4373-1-git-send-email-bemk@redhat.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 Wed, 18 Sep, at 07:28:53PM, Bart Kuivenhoven wrote: > The problem in efi_main was that the idt was cleared before the > interrupts were disabled. > > The UEFI spec states that interrupts aren't used so this shouldn't be > too much of a problem. Peripherals however don't necessarily know about > this and thus might cause interrupts to happen anyway. Even if > ExitBootServices() has been called. > > This means there is a risk of an interrupt being triggered while the IDT > register is nullified and the interrupt bit hasn't been cleared, > allowing for a triple fault. Just to be clear, you haven't witnessed a triple fault, correct? > This patch fixes this by clearing the interrupt bit before the lidt > instruction. I think we can go even further than this and get rid of all of the IDT code in the EFI boot stub. The kernel maintains its own IDT anyway. -- Matt Fleming, Intel Open Source Technology Center