Merge tag 's390-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

[linux-2.6-microblaze.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f0d6887..0905d2c 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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.