linux-kernel - [2.6.27 PATCH] Blacklist DMAR on Intel G31/G33 chipsets

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Date:	Sun, 07 Sep 2008 16:35:26 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, andi@...stfloor.org,
	arjan@...radead.org, torvalds@...ux-foundation.org,
	sfr@...b.auug.org.au, Jesse Barnes <jbarnes@...tuousgeek.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: [2.6.27 PATCH] Blacklist DMAR on Intel G31/G33 chipsets

Some BIOSes (the Intel DG33BU, for example) wrongly claim to have DMAR
when they don't. Avoid the resulting crashes when it doesn't work as
expected.

Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
Acked-by: Ingo Molnar <mingo@...e.hu>

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 8d0e60a..c3edcdc 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -2348,11 +2348,34 @@ static void __init iommu_exit_mempool(void)
 
 }
 
+static int blacklist_iommu(const struct dmi_system_id *id)
+{
+	printk(KERN_INFO "%s detected; disabling IOMMU\n",
+	       id->ident);
+	dmar_disabled = 1;
+	return 0;
+}
+
+static struct dmi_system_id __initdata intel_iommu_dmi_table[] = {
+	{	/* Some DG33BU BIOS revisions advertised non-existent VT-d */
+		.callback = blacklist_iommu,
+		.ident = "Intel DG33BU",
+		{	DMI_MATCH(DMI_BOARD_VENDOR, "Intel Corporation"),
+			DMI_MATCH(DMI_BOARD_NAME, "DG33BU"),
+		}
+	},
+	{ }
+};
+
+
 void __init detect_intel_iommu(void)
 {
 	if (swiotlb || no_iommu || iommu_detected || dmar_disabled)
 		return;
 	if (early_dmar_detect()) {
+		dmi_check_system(intel_iommu_dmi_table);
+		if (dmar_disabled)
+			return;
 		iommu_detected = 1;
 	}
 }


-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation



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