releases/2.6.27.19/fix-intel-iommu-write-buffer-flushing.patch

From ca77fde8e62cecb2c0769052228d15b901367af8 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw2@infradead.org>
Date: Fri, 13 Feb 2009 23:18:03 +0000
Subject: Fix Intel IOMMU write-buffer flushing

From: David Woodhouse <dwmw2@infradead.org>

commit ca77fde8e62cecb2c0769052228d15b901367af8 upstream.

This is the cause of the DMA faults and disk corruption that people have
been seeing. Some chipsets neglect to report the RWBF "capability" --
the flag which says that we need to flush the chipset write-buffer when
changing the DMA page tables, to ensure that the change is visible to
the IOMMU.

Override that bit on the affected chipsets, and everything is happy
again.

Thanks to Chris and Bhavesh and others for helping to debug.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Tested-by: Chris Wright <chrisw@sous-sol.org>
Reviewed-by: Bhavesh Davda <bhavesh@vmware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/pci/intel-iommu.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -72,6 +72,8 @@ static struct deferred_flush_tables *def
 /* bitmap for indexing intel_iommus */
 static int g_num_of_iommus;
 
+static int rwbf_quirk = 0;
+
 static DEFINE_SPINLOCK(async_umap_flush_lock);
 static LIST_HEAD(unmaps_to_do);
 
@@ -527,7 +529,7 @@ static void iommu_flush_write_buffer(str
 	u32 val;
 	unsigned long flag;
 
-	if (!cap_rwbf(iommu->cap))
+	if (!rwbf_quirk && !cap_rwbf(iommu->cap))
 		return;
 	val = iommu->gcmd | DMA_GCMD_WBF;
 
@@ -2453,3 +2455,12 @@ int __init intel_iommu_init(void)
 	return 0;
 }
 
+static void __devinit quirk_iommu_rwbf(struct pci_dev *dev)
+{
+	/* Mobile 4 Series Chipset neglects to set RWBF capability,
+	   but needs it */
+	printk(KERN_INFO "DMAR: Forcing write-buffer flush capability\n");
+	rwbf_quirk = 1;
+}
+
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2a40, quirk_iommu_rwbf);