Messages in this thread Patch in this message | | | From | Lu Baolu <> | Subject | [PATCH 2/2] iommu/vt-d: Avoid unnecessary global DMA cache invalidation | Date | Mon, 19 Sep 2022 14:25:23 +0800 |
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Some VT-d hardware implementations invalidate all DMA remapping hardware translation caches as part of SRTP flow. The VT-d spec adds a ESRTPS (Enhanced Set Root Table Pointer Support, section 11.4.2 in VT-d spec) capability bit to indicate this. With this bit set, software has no need to issue the global invalidation request.
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> --- drivers/iommu/intel/iommu.h | 1 + drivers/iommu/intel/iommu.c | 7 +++++++ 2 files changed, 8 insertions(+)
diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h index 5407d82df4d1..251a609fdce3 100644 --- a/drivers/iommu/intel/iommu.h +++ b/drivers/iommu/intel/iommu.h @@ -146,6 +146,7 @@ /* * Decoding Capability Register */ +#define cap_esrtps(c) (((c) >> 63) & 1) #define cap_esirtps(c) (((c) >> 62) & 1) #define cap_fl5lp_support(c) (((c) >> 60) & 1) #define cap_pi_support(c) (((c) >> 59) & 1) diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 8e5d99197d39..c20f3e060bac 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -1239,6 +1239,13 @@ static void iommu_set_root_entry(struct intel_iommu *iommu) raw_spin_unlock_irqrestore(&iommu->register_lock, flag); + /* + * Hardware invalidates all DMA remapping hardware translation + * caches as part of SRTP flow. + */ + if (cap_esrtps(iommu->cap)) + return; + iommu->flush.flush_context(iommu, 0, 0, 0, DMA_CCMD_GLOBAL_INVL); if (sm_supported(iommu)) qi_flush_pasid_cache(iommu, 0, QI_PC_GLOBAL, 0); -- 2.34.1
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