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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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11
drivers/pci/dmar.c
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@@ -515,6 +515,7 @@ int alloc_iommu(struct dmar_drhd_unit *drhd)
u32 ver;
static int iommu_allocated = 0;
int agaw = 0;
int msagaw = 0;
iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
if (!iommu)
@@ -535,12 +536,20 @@ int alloc_iommu(struct dmar_drhd_unit *drhd)
agaw = iommu_calculate_agaw(iommu);
if (agaw < 0) {
printk(KERN_ERR
"Cannot get a valid agaw for iommu (seq_id = %d)\n",
"Cannot get a valid agaw for iommu (seq_id = %d)\n",
iommu->seq_id);
goto error;
}
msagaw = iommu_calculate_max_sagaw(iommu);
if (msagaw < 0) {
printk(KERN_ERR
"Cannot get a valid max agaw for iommu (seq_id = %d)\n",
iommu->seq_id);
goto error;
}
#endif
iommu->agaw = agaw;
iommu->msagaw = msagaw;
/* the registers might be more than one page */
map_size = max_t(int, ecap_max_iotlb_offset(iommu->ecap),