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diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
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@@ -4992,6 +4992,18 @@
an IOTLB flush. Default is lazy flushing before reuse,
which is faster.
+ s390_iommu_aperture= [KNL,S390]
+ Specifies the size of the per device DMA address space
+ accessible through the DMA and IOMMU APIs as a decimal
+ factor of the size of main memory.
+ The default is 1 meaning that one can concurrently use
+ as many DMA addresses as physical memory is installed,
+ if supported by hardware, and thus map all of memory
+ once. With a value of 2 one can map all of memory twice
+ and so on. As a special case a factor of 0 imposes no
+ restrictions other than those given by hardware at the
+ cost of significant additional memory use for tables.
+
sa1100ir [NET]
See drivers/net/irda/sa1100_ir.c.