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authorKarsten Weiss <K.Weiss@science-computing.de>2007-02-13 13:26:21 +0100
committerAndi Kleen <andi@basil.nowhere.org>2007-02-13 13:26:21 +0100
commit5558870bfbcca10cfc7b13ab866687012ea3c9af (patch)
tree45605429a4fd5eee9b05d5e7c852fa72bfd07a21 /arch/x86_64
parent5809f9d442e9dbb23859e2c37d8c47043f6b5cc9 (diff)
[PATCH] x86-64: improved iommu documentation
- add SWIOTLB config help text - mention Documentation/x86_64/boot-options.txt in Documentation/kernel-parameters.txt - remove the duplication of the iommu kernel parameter documentation. - Better explanation of some of the iommu kernel parameter options. - "32MB<<order" instead of "32MB^order". - Mention the default "order" value. - list the four existing PCI-DMA mapping implementations of arch x86_64 - group the iommu= option keywords by PCI-DMA mapping implementation. - Distinguish iommu= option keywords from number arguments. - Explain the meaning of DAC and SAC. Signed-off-by: Karsten Weiss <knweiss@science-computing.de> Signed-off-by: Andi Kleen <ak@suse.de> Acked-by: Muli Ben-Yehuda <muli@il.ibm.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org>
Diffstat (limited to 'arch/x86_64')
-rw-r--r--arch/x86_64/Kconfig10
-rw-r--r--arch/x86_64/kernel/pci-dma.c28
2 files changed, 12 insertions, 26 deletions
diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 02dd39457bc..a55382a1bb4 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -458,8 +458,8 @@ config IOMMU
on systems with more than 3GB. This is usually needed for USB,
sound, many IDE/SATA chipsets and some other devices.
Provides a driver for the AMD Athlon64/Opteron/Turion/Sempron GART
- based IOMMU and a software bounce buffer based IOMMU used on Intel
- systems and as fallback.
+ based hardware IOMMU and a software bounce buffer based IOMMU used
+ on Intel systems and as fallback.
The code is only active when needed (enough memory and limited
device) unless CONFIG_IOMMU_DEBUG or iommu=force is specified
too.
@@ -496,6 +496,12 @@ config CALGARY_IOMMU_ENABLED_BY_DEFAULT
# need this always selected by IOMMU for the VIA workaround
config SWIOTLB
bool
+ help
+ Support for software bounce buffers used on x86-64 systems
+ which don't have a hardware IOMMU (e.g. the current generation
+ of Intel's x86-64 CPUs). Using this PCI devices which can only
+ access 32-bits of memory can be used on systems with more than
+ 3 GB of memory. If unsure, say Y.
config X86_MCE
bool "Machine check support" if EMBEDDED
diff --git a/arch/x86_64/kernel/pci-dma.c b/arch/x86_64/kernel/pci-dma.c
index 683b7a5c1ab..651ccfb0669 100644
--- a/arch/x86_64/kernel/pci-dma.c
+++ b/arch/x86_64/kernel/pci-dma.c
@@ -223,30 +223,10 @@ int dma_set_mask(struct device *dev, u64 mask)
}
EXPORT_SYMBOL(dma_set_mask);
-/* iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,merge]
- [,forcesac][,fullflush][,nomerge][,biomerge]
- 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 lazy merging. This may improve performance on some block devices.
- Implies force (experimental)
- biomerge Do merging at the BIO layer. This is more efficient than merge,
- but should be only done with very big IOMMUs. Implies merge,force.
- 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
- nodac Forbid DMA >4GB
- panic Force panic when IOMMU overflows
-*/
+/*
+ * See <Documentation/x86_64/boot-options.txt> for the iommu kernel parameter
+ * documentation.
+ */
__init int iommu_setup(char *p)
{
iommu_merge = 1;