diff options
Diffstat (limited to 'Documentation/x86')
| -rw-r--r-- | Documentation/x86/x86_64/boot-options.txt | 13 |
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 b297c48389b9..8d109ef67ab6 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 |