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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
commit 4ed0d3e6c6
10 changed files with 165 additions and 50 deletions
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8
include/linux/dma_remapping.h
View file

@ -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;

2
include/linux/intel-iommu.h
View file

@ -120,6 +120,7 @@ static inline void dmar_writeq(void __iomem *addr, u64 val)
(ecap_iotlb_offset(e) + ecap_niotlb_iunits(e) * 16)
#define ecap_coherent(e) ((e) & 0x1)
#define ecap_qis(e) ((e) & 0x2)
#define ecap_pass_through(e) ((e >> 6) & 0x1)
#define ecap_eim_support(e) ((e >> 4) & 0x1)
#define ecap_ir_support(e) ((e >> 3) & 0x1)
#define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
@ -302,6 +303,7 @@ struct intel_iommu {
spinlock_t register_lock; /* protect register handling */
int seq_id; /* sequence id of the iommu */
int agaw; /* agaw of this iommu */
int msagaw; /* max sagaw of this iommu */
unsigned int irq;
unsigned char name[13]; /* Device Name */