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authorChristoph Hellwig <hch@lst.de>2018-04-27 09:31:47 +0200
committerChristoph Hellwig <hch@lst.de>2018-05-28 12:48:21 +0200
commit098afd981744061d37eb4d40bc3f755438570afb (patch)
treee9086d4732a6c381a03406f4331a8477e2a780a7
parent06e9552f5f12564dc1c3483f0934d96cc4f72f18 (diff)
x86/pci-dma: remove the explicit nodac and allowdac option
This is something drivers should decide (modulo chipset quirks like for VIA), which as far as I can tell is how things have been handled for the last 15 years. Note that we keep the usedac option for now, as it is used in the wild to override the too generic VIA quirk. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--Documentation/x86/x86_64/boot-options.txt5
-rw-r--r--arch/x86/kernel/pci-dma.c4
2 files changed, 2 insertions, 7 deletions
diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index 341588ec4e29..8d109ef67ab6 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -236,11 +236,6 @@ IOMMU (input/output memory management unit)
nomerge Don't do scatter-gather (SG) merging.
noaperture Ask the IOMMU not to touch the aperture for AGP.
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
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index b65b0d7072f1..b523414bc323 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -122,9 +122,9 @@ static __init int iommu_setup(char *p)
if (!strncmp(p, "forcesac", 8))
pr_warn("forcesac option ignored.\n");
if (!strncmp(p, "allowdac", 8))
- forbid_dac = 0;
+ pr_warn("allowdac option ignored.\n");
if (!strncmp(p, "nodac", 5))
- forbid_dac = 1;
+ pr_warn("nodac option ignored.\n");
if (!strncmp(p, "usedac", 6)) {
forbid_dac = -1;
return 1;