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authorChristoph Hellwig <hch@lst.de>2018-04-27 09:13:24 +0200
committerChristoph Hellwig <hch@lst.de>2018-05-28 12:48:16 +0200
commit06e9552f5f12564dc1c3483f0934d96cc4f72f18 (patch)
tree48c92eba3b3c1a7e8576fc84159183481e5e2960 /Documentation
parent84564d1c76255ac6d5fb76c85818cb5961fad061 (diff)
downloadlinux-06e9552f5f12564dc1c3483f0934d96cc4f72f18.tar.bz2
x86/pci-dma: remove the experimental forcesac boot option
Limiting the dma mask to avoid PCI (pre-PCIe) DAC cycles while paying the huge overhead of an IOMMU is rather pointless, and this seriously gets in the way of dma mapping work. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt1
-rw-r--r--Documentation/x86/x86_64/boot-options.txt4
2 files changed, 1 insertions, 4 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 11fc28ecdb6d..6d4a666748dd 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1705,7 +1705,6 @@
nopanic
merge
nomerge
- forcesac
soft
pt [x86, IA-64]
nobypass [PPC/POWERNV]
diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index 153b3a57fba2..341588ec4e29 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -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:
@@ -235,8 +235,6 @@ 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