Hi Jacob, On Fri, May 19, 2023 at 01:32:20PM -0700, Jacob Pan wrote: > PCIe Process address space ID (PASID) is used to tag DMA traffic, it > provides finer grained isolation than requester ID (RID). > > For each RID, 0 is as a special PASID for the legacy DMA (without > PASID), thus RID_PASID. This is universal across all architectures, > therefore warranted to be declared in the common header. > Noting that VT-d could support none-zero RID_PASID, but currently not > used. > > By having a common RID_PASID, we can avoid conflicts between different > use cases in the generic code. e.g. SVA and DMA API with PASIDs. > > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> > --- > v6: > - let SMMU code use the common RID_PASID macro > --- > .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 2 +- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 10 ++++---- > drivers/iommu/intel/iommu.c | 24 +++++++++---------- > drivers/iommu/intel/pasid.c | 2 +- > drivers/iommu/intel/pasid.h | 1 - > include/linux/iommu.h | 1 + > 6 files changed, 20 insertions(+), 20 deletions(-) > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c > index a5a63b1c947e..160b31e6239d 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c > @@ -80,7 +80,7 @@ arm_smmu_share_asid(struct mm_struct *mm, u16 asid) > * be some overlap between use of both ASIDs, until we invalidate the > * TLB. > */ > - arm_smmu_write_ctx_desc(smmu_domain, 0, cd); > + arm_smmu_write_ctx_desc(smmu_domain, IOMMU_DEF_RID_PASID, cd); I agree with reserving 0 globally for non-PASID DMA, but could we call this something more generic, like IOMMU_NO_PASID? The term "RID_PASID" is specific to VT-d and "RID" to PCI, so it looks confusing here (this driver also supports non-PCI). "NO_PASID" would be clearer to someone just trying to follow this driver code. Thanks, Jean
