From 098afd981744061d37eb4d40bc3f755438570afb Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 27 Apr 2018 09:31:47 +0200 Subject: [PATCH] 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 Reviewed-by: Thomas Gleixner --- Documentation/x86/x86_64/boot-options.txt | 5 ----- arch/x86/kernel/pci-dma.c | 4 ++-- 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; -- GitLab