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-rw-r--r--Documentation/x86/x86_64/boot-options.txt13
1 files changed, 3 insertions, 10 deletions
diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index b297c48389b92..8d109ef67ab6b 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -187,9 +187,9 @@ PCI
IOMMU (input/output memory management unit)
- Currently four x86-64 PCI-DMA mapping implementations exist:
+ Multiple x86-64 PCI-DMA mapping implementations exist, for example:
- 1. <arch/x86_64/kernel/pci-nommu.c>: use no hardware/software IOMMU at all
+ 1. <lib/dma-direct.c>: use no hardware/software IOMMU at all
(e.g. because you have < 3 GB memory).
Kernel boot message: "PCI-DMA: Disabling IOMMU"
@@ -208,7 +208,7 @@ IOMMU (input/output memory management unit)
Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
- [,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge]
+ [,memaper[=<order>]][,merge][,fullflush][,nomerge]
[,noaperture][,calgary]
General iommu options:
@@ -235,14 +235,7 @@ IOMMU (input/output memory management unit)
(experimental).
nomerge Don't do scatter-gather (SG) merging.
noaperture Ask the IOMMU not to touch the aperture for AGP.
- forcesac Force single-address cycle (SAC) mode for masks <40bits
- (experimental).
noagp Don't initialize the AGP driver and use full aperture.
- allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
- DAC is used with 32-bit PCI to push a 64-bit address in
- two cycles. When off all DMA over >4GB is forced through
- an IOMMU or software bounce buffering.
- nodac Forbid DAC mode, i.e. DMA >4GB.
panic Always panic when IOMMU overflows.
calgary Use the Calgary IOMMU if it is available