[PATCH kernel] powerpc/powernv/ioda: Fix endianness when reading TCEs

[Alexey Kardashevskiy <aik@ozlabs.ru>]

The iommu_table_ops::exchange() callback writes new TCE to the table
and returns old value and permission mask. The old TCE value is
correctly converted from BE to CPU endian; however permission mask
was calculated from BE value and therefore always returned DMA_NONE
which could cause memory leak on LE systems using VFIO SPAPR TCE IOMMU v1
driver.

This fixes pnv_tce_xchg() to have @oldtce a CPU endian.

Fixes: 05c6cfb9dce0d13d37e9d007ee6a4af36f1c0a58
Cc: stable@vger.kernel.org # 4.2+
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 arch/powerpc/platforms/powernv/pci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 1d92bd9..7b17f88 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -620,8 +620,8 @@ int pnv_tce_xchg(struct iommu_table *tbl, long index,
 	if (newtce & TCE_PCI_WRITE)
 		newtce |= TCE_PCI_READ;
 
-	oldtce = xchg(pnv_tce(tbl, idx), cpu_to_be64(newtce));
-	*hpa = be64_to_cpu(oldtce) & ~(TCE_PCI_READ | TCE_PCI_WRITE);
+	oldtce = be64_to_cpu(xchg(pnv_tce(tbl, idx), cpu_to_be64(newtce)));
+	*hpa = oldtce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
 	*direction = iommu_tce_direction(oldtce);
 
 	return 0;
-- 
2.5.0.rc3