[PATCH] Allow disabling DAC using command line options

Might or might not work around some reported bugs on VIA systems.

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 4303e0c12476..e97a4c8fe6ea 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]