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-rw-r--r--Documentation/x86_64/boot-options.txt4
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 4303e0c1247..e97a4c8fe6e 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -199,6 +199,10 @@ IOMMU
allowed overwrite iommu off workarounds for specific chipsets.
soft Use software bounce buffering (default for Intel machines)
noaperture Don't touch the aperture for AGP.
+ allowdac Allow DMA >4GB
+ When off all DMA over >4GB is forced through an IOMMU or bounce
+ buffering.
+ nodac Forbid DMA >4GB
swiotlb=pages[,force]