Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262911AbTHUUw3 (ORCPT ); Thu, 21 Aug 2003 16:52:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262916AbTHUUw3 (ORCPT ); Thu, 21 Aug 2003 16:52:29 -0400 Received: from sccrmhc13.comcast.net ([204.127.202.64]:10133 "EHLO sccrmhc13.comcast.net") by vger.kernel.org with ESMTP id S262911AbTHUUwZ (ORCPT ); Thu, 21 Aug 2003 16:52:25 -0400 Subject: [PATCH] Pentium Pro - sysenter - doublefault From: Jim Houston Reply-To: jim.houston@comcast.net To: linux-kernel@vger.kernel.org Cc: jim.houston@ccur.com Content-Type: text/plain; charset=UTF-8 Organization: Message-Id: <1061498486.3072.308.camel@new.localdomain> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.2 (1.2.2-4) Date: 21 Aug 2003 16:41:26 -0400 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2130 Lines: 58 Hi Everyone, I upgraded my Pentium Pro system to Redhat 9, installed a linux-2.6.0-test3 kernel, and it fails with a double-fault when init starts. The code which decides if it is o.k. to use sysenter is broken for some Pentium Pro cpus ,in particular, this bit of code from arch/i386/kernel/cpu/intel.c: /* SEP CPUID bug: Pentium Pro reports SEP but doesn't have it */ if ( c->x86 == 6 && c->x86_model < 3 && c->x86_mask < 3 ) clear_bit(X86_FEATURE_SEP, c->x86_capability); On my cpu model=1 and mask=9, it doesn't clear 86_FEATURE_SEP. This results in a double-fault when init starts. The double-fault happens on the sysexit. The new double-fault handler caught this nicely, and I was able to debug this with kgdb. The logic above is exactly what Intel says to do in "IA-32 Intel® Architecture Software Developer's Manual, Volume 2: Instruction Set Reference" on page 3-767. It also says that sysenter was added to the Pentium II. I checked the Pentium Pro and Pentium II Specifications Update manuals hoping to find the details to justify the "mask < 3" portion of the test above. They both describe sysenter related errata but none which was fixed in mask 3. The attached patch avoids using sysenter on all Pentium Pro systems. Jim Houston - Concurrent Computer Corp. diff -urN linux-2.6.0-test3.orig/arch/i386/kernel/cpu/intel.c linux-2.6.0-test3.new/arch/i386/kernel/cpu/intel.c --- linux-2.6.0-test3.orig/arch/i386/kernel/cpu/intel.c 2003-08-20 10:30:14.000000000 -0400 +++ linux-2.6.0-test3.new/arch/i386/kernel/cpu/intel.c 2003-08-21 14:39:35.000000000 -0400 @@ -246,7 +246,7 @@ } /* SEP CPUID bug: Pentium Pro reports SEP but doesn't have it */ - if ( c->x86 == 6 && c->x86_model < 3 && c->x86_mask < 3 ) + if ( c->x86 == 6 && c->x86_model < 3) clear_bit(X86_FEATURE_SEP, c->x86_capability); /* Names for the Pentium II/Celeron processors - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/