bfd20f1cc8
IOMMU harms performance signficantly when we run very fast networking workloads. It's 40GB networking doing XDP test. Software overhead is almost unaware, but it's the IOTLB miss (based on our analysis) which kills the performance. We observed the same performance issue even with software passthrough (identity mapping), only the hardware passthrough survives. The pps with iommu (with software passthrough) is only about ~30% of that without it. This is a limitation in hardware based on our observation, so we'd like to disable the IOMMU force on, but we do want to use TBOOT and we can sacrifice the DMA security bought by IOMMU. I must admit I know nothing about TBOOT, but TBOOT guys (cc-ed) think not eabling IOMMU is totally ok. So introduce a new boot option to disable the force on. It's kind of silly we need to run into intel_iommu_init even without force on, but we need to disable TBOOT PMR registers. For system without the boot option, nothing is changed. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
58 lines
1.4 KiB
C
58 lines
1.4 KiB
C
#ifndef _DMA_REMAPPING_H
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#define _DMA_REMAPPING_H
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/*
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* VT-d hardware uses 4KiB page size regardless of host page size.
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*/
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#define VTD_PAGE_SHIFT (12)
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#define VTD_PAGE_SIZE (1UL << VTD_PAGE_SHIFT)
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#define VTD_PAGE_MASK (((u64)-1) << VTD_PAGE_SHIFT)
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#define VTD_PAGE_ALIGN(addr) (((addr) + VTD_PAGE_SIZE - 1) & VTD_PAGE_MASK)
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#define VTD_STRIDE_SHIFT (9)
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#define VTD_STRIDE_MASK (((u64)-1) << VTD_STRIDE_SHIFT)
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#define DMA_PTE_READ (1)
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#define DMA_PTE_WRITE (2)
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#define DMA_PTE_LARGE_PAGE (1 << 7)
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#define DMA_PTE_SNP (1 << 11)
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#define CONTEXT_TT_MULTI_LEVEL 0
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#define CONTEXT_TT_DEV_IOTLB 1
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#define CONTEXT_TT_PASS_THROUGH 2
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/* Extended context entry types */
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#define CONTEXT_TT_PT_PASID 4
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#define CONTEXT_TT_PT_PASID_DEV_IOTLB 5
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#define CONTEXT_TT_MASK (7ULL << 2)
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#define CONTEXT_DINVE (1ULL << 8)
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#define CONTEXT_PRS (1ULL << 9)
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#define CONTEXT_PASIDE (1ULL << 11)
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struct intel_iommu;
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struct dmar_domain;
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struct root_entry;
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#ifdef CONFIG_INTEL_IOMMU
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extern int iommu_calculate_agaw(struct intel_iommu *iommu);
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extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
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extern int dmar_disabled;
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extern int intel_iommu_enabled;
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extern int intel_iommu_tboot_noforce;
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#else
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static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
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{
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return 0;
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}
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static inline int iommu_calculate_max_sagaw(struct intel_iommu *iommu)
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{
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return 0;
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}
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#define dmar_disabled (1)
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#define intel_iommu_enabled (0)
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#endif
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#endif
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