From: Don Dutile <ddutile@redhat.com>
Date: Tue, 1 Dec 2009 23:43:41 -0500
Subject: [pci] intel-iommu: set dmar_disabled when DMAR at zero
Message-id: <4B15AA2D.2020507@redhat.com>
Patchwork-id: 21636
O-Subject: [RHEL5.5 PATCH V2] 8/9:  intel-iommu: set dmar_disabled when DMAR
	at zero
Bugzilla: 516811 518103
RH-Acked-by: Chris Wright <chrisw@redhat.com>
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>

V2:  cleaned out indent fixes (moved to 1/9 or 2/9) so
      it's just the original patch backported.

bz 516727.

The attachment makes one wonder what upstream testers
tested!
David Woodhouse doesn't understand how patch 4/9 could
have worked without this patch.
Kept is spearate since that's how it was done, and easy to backport in.

0/9 states build & tests.

Please review and ACK.

- Don
>From 61f48a1787d14e44fe8ec291ca2d94d58d02902b Mon Sep 17 00:00:00 2001
From: Donald Dutile <ddutile@redhat.com>
Date: Fri, 20 Nov 2009 14:45:43 -0500
Subject: [PATCH 8/9] intel-iommu: set dmar_disabled when DMAR at zero

>From email to Linus, fwd by David Woodhouse;
patch for bz 533952 (for F12).

Commit 86cf898e1d0fca245173980e3897580db38569a8 ("intel-iommu: Check for
'DMAR at zero' BIOS error earlier.") was supposed to work by pretending
not to detect an IOMMU if it was actually being reported by the BIOS at
physical address zero.

However, the IOMMU detection and init code is all a little baroque, and
the IOMMU ended up getting initialised _anyway_.

I don't have one of the offending machines to hand, at least three
testers reported that the original patch did actually fix the problem
and allow their machines to boot.

I have no clue how they came to that conclusion.

This patch also sets the dmar_disabled flag when the error is detected,
so that when we're later asked to initialise the IOMMU that we never
claimed to have detected, we refuse to do so.

diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index aa96ce2..228198c 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -595,6 +595,9 @@ int __init check_zero_address(void)
 					dmi_get_system_info(DMI_BIOS_VENDOR),
 					dmi_get_system_info(DMI_BIOS_VERSION),
 					dmi_get_system_info(DMI_PRODUCT_VERSION));
+#ifdef CONFIG_DMAR
+				dmar_disabled = 1;
+#endif
 				return 0;
 			}
 			break;