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Intel IOMMU Pass Through Support

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The patch adds kernel parameter intel_iommu=pt to set up pass through
mode in context mapping entry. This disables DMAR in linux kernel; but
KVM still runs on VT-d and interrupt remapping still works.

In this mode, kernel uses swiotlb for DMA API functions but other VT-d
functionalities are enabled for KVM. KVM always uses multi level
translation page table in VT-d. By default, pass though mode is disabled
in kernel.

This is useful when people don't want to enable VT-d DMAR in kernel but
still want to use KVM and interrupt remapping for reasons like DMAR
performance concern or debug purpose.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Weidong Han <weidong@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
Fenghua Yu
2009-04-24 17:30:20 -07:00
committed by David Woodhouse
parent 0910697403
commit 4ed0d3e6c6
10 changed files with 166 additions and 51 deletions
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6
arch/x86/kernel/pci-dma.c
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@ -160,6 +160,8 @@ again:
return page_address(page);
}
extern int iommu_pass_through;
/*
* See <Documentation/x86_64/boot-options.txt> for the iommu kernel parameter
* documentation.
@ -209,6 +211,10 @@ static __init int iommu_setup(char *p)
#ifdef CONFIG_SWIOTLB
if (!strncmp(p, "soft", 4))
swiotlb = 1;
if (!strncmp(p, "pt", 2)) {
iommu_pass_through = 1;
return 1;
}
#endif
gart_parse_options(p);