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authorFenghua Yu <fenghua.yu@intel.com>2009-04-24 17:30:20 -0700
committerDavid Woodhouse <David.Woodhouse@intel.com>2009-04-29 06:54:34 +0100
commit4ed0d3e6c64cfd9ba4ceb2099b10d1cf8ece4320 (patch)
tree950bacfaf57040aafbcc2ea9b52eb171d35c23bd /arch/x86
parent091069740304c979f957ceacec39c461d0192158 (diff)
downloadop-kernel-dev-4ed0d3e6c64cfd9ba4ceb2099b10d1cf8ece4320.zip
op-kernel-dev-4ed0d3e6c64cfd9ba4ceb2099b10d1cf8ece4320.tar.gz
Intel IOMMU Pass Through Support
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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/iommu.h1
-rw-r--r--arch/x86/kernel/pci-dma.c6
-rw-r--r--arch/x86/kernel/pci-swiotlb.c3
3 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h
index af326a2..fd6d21b 100644
--- a/arch/x86/include/asm/iommu.h
+++ b/arch/x86/include/asm/iommu.h
@@ -6,6 +6,7 @@ extern void no_iommu_init(void);
extern struct dma_map_ops nommu_dma_ops;
extern int force_iommu, no_iommu;
extern int iommu_detected;
+extern int iommu_pass_through;
/* 10 seconds */
#define DMAR_OPERATION_TIMEOUT ((cycles_t) tsc_khz*10*1000)
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 745579b..8cad0d8 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -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);
diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index 221a385..3a0c51e 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -71,7 +71,8 @@ void __init pci_swiotlb_init(void)
{
/* don't initialize swiotlb if iommu=off (no_iommu=1) */
#ifdef CONFIG_X86_64
- if (!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN)
+ if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) ||
+ iommu_pass_through)
swiotlb = 1;
#endif
if (swiotlb_force)
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