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Commit ece66840 authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen
Browse files

[PATCH] Allow disabling DAC using command line options 



Might or might not work around some reported bugs on VIA systems.

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent b885808e

Documentation/x86_64/boot-options.txt

+4 −0
Original line number Diff line number Diff line
@@ -199,6 +199,10 @@ IOMMU 
   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



  swiotlb=pages[,force]

arch/x86_64/kernel/pci-dma.c

+18 −0
Original line number Diff line number Diff line
@@ -170,8 +170,20 @@ void dma_free_coherent(struct device *dev, size_t size, 
}

EXPORT_SYMBOL(dma_free_coherent);



static int forbid_dac __read_mostly;



int dma_supported(struct device *dev, u64 mask)

{

#ifdef CONFIG_PCI

	if (mask > 0xffffffff && forbid_dac > 0) {







		printk(KERN_INFO "PCI: Disallowing DAC for device %s\n", dev->bus_id);

		return 0;

	}

#endif



	if (dma_ops->dma_supported)

		return dma_ops->dma_supported(dev, mask);
@@ -231,6 +243,8 @@ EXPORT_SYMBOL(dma_set_mask); 
   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

*/

__init int iommu_setup(char *p)

{
@@ -267,6 +281,10 @@ __init int iommu_setup(char *p) 
		    iommu_merge = 0;

	    if (!strncmp(p, "forcesac",8))

		    iommu_sac_force = 1;

	    if (!strncmp(p, "allowdac", 8))

		    forbid_dac = 0;

	    if (!strncmp(p, "nodac", 5))

		    forbid_dac = -1;



#ifdef CONFIG_SWIOTLB

	    if (!strncmp(p, "soft",4))