powernv/iommu: disable IOMMU bypass with param iommu=nobypass
When IOMMU bypass is enabled, a PCI device can read and write memory
that was not mapped by the driver without causing an EEH. That might
cause memory corruption, for example.
When we disable bypass, DMA reads and writes to addresses not mapped by
the IOMMU will cause an EEH, allowing us to debug such issues.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4df73da..7dedfe5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1493,6 +1493,8 @@
forcesac
soft
pt [x86, IA-64]
+ nobypass [PPC/POWERNV]
+ Disable IOMMU bypass, using IOMMU for PCI devices.
io7= [HW] IO7 for Marvel based alpha systems