From: Joerg Roedel <jroe...@suse.de>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit e6aabee05f41c9d18e0b92194819edd84f352ac9 upstream.

Handle this case to make sure boundary_size does not become
0 and trigger a BUG_ON later.

Signed-off-by: Joerg Roedel <jroe...@suse.de>
Signed-off-by: Jiri Slaby <jsl...@suse.cz>
---
 drivers/iommu/amd_iommu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index b853bb47fc7d..d22b4af761f5 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1750,14 +1750,16 @@ static unsigned long dma_ops_area_alloc(struct device 
*dev,
        unsigned long next_bit = dom->next_address % APERTURE_RANGE_SIZE;
        int max_index = dom->aperture_size >> APERTURE_RANGE_SHIFT;
        int i = start >> APERTURE_RANGE_SHIFT;
-       unsigned long boundary_size;
+       unsigned long boundary_size, mask;
        unsigned long address = -1;
        unsigned long limit;
 
        next_bit >>= PAGE_SHIFT;
 
-       boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1,
-                       PAGE_SIZE) >> PAGE_SHIFT;
+       mask = dma_get_seg_boundary(dev);
+
+       boundary_size = mask + 1 ? ALIGN(mask + 1, PAGE_SIZE) >> PAGE_SHIFT :
+                                  1UL << (BITS_PER_LONG - PAGE_SHIFT);
 
        for (;i < max_index; ++i) {
                unsigned long offset = dom->aperture[i]->offset >> PAGE_SHIFT;
-- 
2.6.2

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