Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752973AbYL3QUY (ORCPT ); Tue, 30 Dec 2008 11:20:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751580AbYL3QUL (ORCPT ); Tue, 30 Dec 2008 11:20:11 -0500 Received: from host64.cybernetics.com ([98.174.209.230]:2053 "EHLO mail.cybernetics.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501AbYL3QUK (ORCPT ); Tue, 30 Dec 2008 11:20:10 -0500 Message-ID: <495A4A39.20903@cybernetics.com> Date: Tue, 30 Dec 2008 11:20:09 -0500 From: Tony Battersby User-Agent: Thunderbird 2.0.0.18 (X11/20081125) MIME-Version: 1.0 To: avi@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] [DMAR] Fix endless "Unknown DMAR structure type" loop Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2654 Lines: 63 I have a SuperMicro C2SBX motherboard with BIOS revision 1.0b. With vt-d enabled in the BIOS, Linux gets into an endless loop printing "DMAR:Unknown DMAR structure type" when booting. Here is the DMAR ACPI table: DMAR @ 0x7fe86dec 0000: 44 4d 41 52 98 00 00 00 01 6f 49 6e 74 65 6c 20 DMAR.....oIntel 0010: 4f 45 4d 44 4d 41 52 20 00 00 04 06 4c 4f 48 52 OEMDMAR ....LOHR 0020: 01 00 00 00 23 00 00 00 00 00 00 00 00 00 00 00 ....#........... 0030: 01 00 58 00 00 00 00 00 00 a0 e8 7f 00 00 00 00 ..X............. 0040: ff ff ef 7f 00 00 00 00 01 08 00 00 00 00 1d 00 ................ 0050: 01 08 00 00 00 00 1d 01 01 08 00 00 00 00 1d 02 ................ 0060: 01 08 00 00 00 00 1d 07 01 08 00 00 00 00 1a 00 ................ 0070: 01 08 00 00 00 00 1a 01 01 08 00 00 00 00 1a 02 ................ 0080: 01 08 00 00 00 00 1a 07 01 08 00 00 00 00 1a 07 ................ 0090: c0 00 68 00 04 10 66 60 ..h...f` Here are the messages printed by the kernel: DMAR:Host address width 36 DMAR:RMRR base: 0x000000007fe8a000 end: 0x000000007fefffff DMAR:Unknown DMAR structure type DMAR:Unknown DMAR structure type DMAR:Unknown DMAR structure type ... Although I not very familiar with ACPI, to me it looks like struct acpi_dmar_header::length == 0x0058 is incorrect, causing parse_dmar_table() to look at an invalid offset on the next loop. This offset happens to have struct acpi_dmar_header::length == 0x0000, which prevents the loop from ever terminating. This patch checks for this condition and bails out instead of looping forever. Signed-off-by: Tony Battersby --- I previously sent this to linux-acpi on August 18, 2008, but got no reply. Please apply this patch upstream (2.6.29 if possible). --- linux-2.6.28-git2/drivers/pci/dmar.c.orig 2008-12-24 18:26:37.000000000 -0500 +++ linux-2.6.28-git2/drivers/pci/dmar.c 2008-12-30 11:01:17.000000000 -0500 @@ -339,6 +339,14 @@ parse_dmar_table(void) entry_header = (struct acpi_dmar_header *)(dmar + 1); while (((unsigned long)entry_header) < (((unsigned long)dmar) + dmar_tbl->length)) { + /* Avoid looping forever on bad ACPI tables */ + if (entry_header->length == 0) { + printk(KERN_WARNING PREFIX + "Invalid 0-length structure\n"); + ret = -EINVAL; + break; + } + dmar_table_print_dmar_entry(entry_header); switch (entry_header->type) { -- 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/