s390/pci: introduce lazy IOTLB flushing for DMA unmap
This changes the default IOTLB flushing method to lazy flushing, which
means that there will be no direct flush after each DMA unmap operation.
Instead, the iommu bitmap pointer will be adjusted after unmap, so that
no DMA address will be re-used until after an iommu bitmap wrap-around.
The only IOTLB flush will then happen after each wrap-around.
A new kernel parameter "s390_iommu=" is also introduced, to allow changing
the flushing behaviour to the old strict method.
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b7fa2f5..c848095 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3023,6 +3023,13 @@
S [KNL] Run init in single mode
+ s390_iommu= [HW,S390]
+ Set s390 IOTLB flushing mode
+ strict
+ With strict flushing every unmap operation will result in
+ an IOTLB flush. Default is lazy flushing before reuse,
+ which is faster.
+
sa1100ir [NET]
See drivers/net/irda/sa1100_ir.c.