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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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8
include/linux/dma_remapping.h
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@ -13,6 +13,9 @@
#define DMA_PTE_WRITE (2)
#define DMA_PTE_SNP (1 << 11)
#define CONTEXT_TT_MULTI_LEVEL 0
#define CONTEXT_TT_PASS_THROUGH 2
struct intel_iommu;
struct dmar_domain;
struct root_entry;
@ -21,11 +24,16 @@ extern void free_dmar_iommu(struct intel_iommu *iommu);
#ifdef CONFIG_DMAR
extern int iommu_calculate_agaw(struct intel_iommu *iommu);
extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
#else
static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
{
return 0;
}
static inline int iommu_calculate_max_sagaw(struct intel_iommu *iommu)
{
return 0;
}
#endif
extern int dmar_disabled;