[PATCH] ppc/iommu: prevent false TCE leak message

Thadeu Lima de Souza Cascardo cascardo at linux.vnet.ibm.com
Fri Dec 28 03:28:06 EST 2012

When a device DMA window includes the address 0, it's reserved in the
TCE bitmap to avoid returning that address to drivers.

When the device is removed, the bitmap is checked for any mappings not
removed by the driver, indicating a possible DMA mapping leak. Since the
reserved address is not cleared, a message is printed, warning of such a

Check for the reservation, and clear it before checking for any other
standing mappings.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at linux.vnet.ibm.com>
 arch/powerpc/kernel/iommu.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 8226c6c..226e9e5 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -717,6 +717,11 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
+	/* In case we have reserved the first bit, we should not emit
+	 * the warning below. */
+	if (tbl->it_offset == 0)
+		clear_bit(0, tbl->it_map);
 	/* verify that table contains no entries */
 	/* it_size is in entries, and we're examining 64 at a time */
 	for (i = 0; i < (tbl->it_size/64); i++) {

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