linux-kernel - [04/89] intel-iommu: Check for identity mapping candidate using

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Date:	Wed, 15 Jun 2011 16:59:27 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Mike Travis <travis@....com>,
	David Woodhouse <David.Woodhouse@...el.com>
Subject: [04/89] intel-iommu: Check for identity mapping candidate using

2.6.39-stable review patch.  If anyone has any objections, please let us know.

------------------
 system dma mask

From: Chris Wright <chrisw@...s-sol.org>

commit 8fcc5372fbac085199d84a880503ed67aba3fe49 upstream.

The identity mapping code appears to make the assumption that if the
devices dma_mask is greater than 32bits the device can use identity
mapping.  But that is not true: take the case where we have a 40bit
device in a 44bit architecture. The device can potentially receive a
physical address that it will truncate and cause incorrect addresses
to be used.

Instead check to see if the device's dma_mask is large enough
to address the system's dma_mask.

Signed-off-by: Mike Travis <travis@....com>
Reviewed-by: Mike Habeck <habeck@....com>
Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/pci/intel-iommu.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -2190,8 +2190,19 @@ static int iommu_should_identity_map(str
 	 * Assume that they will -- if they turn out not to be, then we can 
 	 * take them out of the 1:1 domain later.
 	 */
-	if (!startup)
-		return pdev->dma_mask > DMA_BIT_MASK(32);
+	if (!startup) {
+		/*
+		 * If the device's dma_mask is less than the system's memory
+		 * size then this is not a candidate for identity mapping.
+		 */
+		u64 dma_mask = pdev->dma_mask;
+
+		if (pdev->dev.coherent_dma_mask &&
+		    pdev->dev.coherent_dma_mask < dma_mask)
+			dma_mask = pdev->dev.coherent_dma_mask;
+
+		return dma_mask >= dma_get_required_mask(&pdev->dev);
+	}
 
 	return 1;
 }


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