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| author | Shaohua Li <shli@fb.com> | 2017-04-26 09:18:35 -0700 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2017-04-26 23:57:53 +0200 |
| commit | bfd20f1cc85010d2f2d77e544da05cd8c149ba9b (patch) | |
| tree | 1da8f1e85622fbf83264b356e1a840c0639b9b65 /include/linux/dma_remapping.h | |
| parent | 161b28aae1651aa7ad63ec14753aa8a751154340 (diff) | |
| download | linux-0-day-bfd20f1cc85010d2f2d77e544da05cd8c149ba9b.tar.gz linux-0-day-bfd20f1cc85010d2f2d77e544da05cd8c149ba9b.tar.xz | |
x86, iommu/vt-d: Add an option to disable Intel IOMMU force on
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>
Diffstat (limited to 'include/linux/dma_remapping.h')
| -rw-r--r-- | include/linux/dma_remapping.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/dma_remapping.h b/include/linux/dma_remapping.h index 187c102997226..90884072fa732 100644 --- a/include/linux/dma_remapping.h +++ b/include/linux/dma_remapping.h @@ -39,6 +39,7 @@ extern int iommu_calculate_agaw(struct intel_iommu *iommu); extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu); extern int dmar_disabled; extern int intel_iommu_enabled; +extern int intel_iommu_tboot_noforce; #else static inline int iommu_calculate_agaw(struct intel_iommu *iommu) { |