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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2014-07-18 19:37:08 +0400
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2014-07-22 11:26:24 +0400
commitc60d1ae4efcb5790f7d085369baf66c167a6484f (patch)
tree7555d2b2e44a6ad6f07e16afaf15492b862d8f99 /Documentation/kernel-parameters.txt
parent29b8dd9d4274bca6526e4bb8d4f46dec1f4c15c9 (diff)
downloadlinux-c60d1ae4efcb5790f7d085369baf66c167a6484f.tar.xz
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>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
-rw-r--r--Documentation/kernel-parameters.txt7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b7fa2f599459..c848095f2cb0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3023,6 +3023,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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.