diff options
Diffstat (limited to 'Documentation/x86_64/boot-options.txt')
| -rw-r--r-- | Documentation/x86_64/boot-options.txt | 109 |
1 files changed, 75 insertions, 34 deletions
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt index 5c86ed6f0448..0d653993f361 100644 --- a/Documentation/x86_64/boot-options.txt +++ b/Documentation/x86_64/boot-options.txt @@ -180,40 +180,81 @@ PCI pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says. pci=noacpi Don't use ACPI to set up PCI interrupt routing. -IOMMU - - iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,merge] - [,forcesac][,fullflush][,nomerge][,noaperture][,calgary] - size set size of iommu (in bytes) - noagp don't initialize the AGP driver and use full aperture. - off don't use the IOMMU - leak turn on simple iommu leak tracing (only when CONFIG_IOMMU_LEAK is on) - memaper[=order] allocate an own aperture over RAM with size 32MB^order. - noforce don't force IOMMU usage. Default. - force Force IOMMU. - merge Do SG merging. Implies force (experimental) - nomerge Don't do SG merging. - forcesac For SAC mode for masks <40bits (experimental) - fullflush Flush IOMMU on each allocation (default) - nofullflush Don't use IOMMU fullflush - 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 - panic Always panic when IOMMU overflows - calgary Use the Calgary IOMMU if it is available - - swiotlb=pages[,force] - - pages Prereserve that many 128K pages for the software IO bounce buffering. - force Force all IO through the software TLB. - - calgary=[64k,128k,256k,512k,1M,2M,4M,8M] - calgary=[translate_empty_slots] - calgary=[disable=<PCI bus number>] +IOMMU (input/output memory management unit) + + Currently four x86-64 PCI-DMA mapping implementations exist: + + 1. <arch/x86_64/kernel/pci-nommu.c>: use no hardware/software IOMMU at all + (e.g. because you have < 3 GB memory). + Kernel boot message: "PCI-DMA: Disabling IOMMU" + + 2. <arch/x86_64/kernel/pci-gart.c>: AMD GART based hardware IOMMU. + Kernel boot message: "PCI-DMA: using GART IOMMU" + + 3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used + e.g. if there is no hardware IOMMU in the system and it is need because + you have >3GB memory or told the kernel to us it (iommu=soft)) + Kernel boot message: "PCI-DMA: Using software bounce buffering + for IO (SWIOTLB)" + + 4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM + pSeries and xSeries servers. This hardware IOMMU supports DMA address + mapping with memory protection, etc. + 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] + [,noaperture][,calgary] + + General iommu options: + off Don't initialize and use any kind of IOMMU. + noforce Don't force hardware IOMMU usage when it is not needed. + (default). + force Force the use of the hardware IOMMU even when it is + not actually needed (e.g. because < 3 GB memory). + soft Use software bounce buffering (SWIOTLB) (default for + Intel machines). This can be used to prevent the usage + of an available hardware IOMMU. + + iommu options only relevant to the AMD GART hardware IOMMU: + <size> Set the size of the remapping area in bytes. + allowed Overwrite iommu off workarounds for specific chipsets. + fullflush Flush IOMMU on each allocation (default). + nofullflush Don't use IOMMU fullflush. + leak Turn on simple iommu leak tracing (only when + CONFIG_IOMMU_LEAK is on). Default number of leak pages + is 20. + memaper[=<order>] Allocate an own aperture over RAM with size 32MB<<order. + (default: order=1, i.e. 64MB) + merge Do scather-gather (SG) merging. Implies "force" + (experimental). + nomerge Don't do scather-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 + + iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU + implementation: + swiotlb=<pages>[,force] + <pages> Prereserve that many 128K pages for the software IO + bounce buffering. + force Force all IO through the software TLB. + + Settings for the IBM Calgary hardware IOMMU currently found in IBM + pSeries and xSeries machines: + + calgary=[64k,128k,256k,512k,1M,2M,4M,8M] + calgary=[translate_empty_slots] + calgary=[disable=<PCI bus number>] + panic Always panic when IOMMU overflows 64k,...,8M - Set the size of each PCI slot's translation table when using the Calgary IOMMU. This is the size of the translation |