On 2023/6/8 15:14, Liu, Yi L wrote:
stage-1 page table cache
invalidation
- @IOMMU_VTD_QI_FLAGS_LEAF: The LEAF flag indicates whether only the
leaf PTE caching needs to be invalidated
and other paging structure caches can be
preserved.- */
what about "Drain Reads" and "Drain Writes"? Is the user allowed/required to provide those hints?
All other comments got. For these two hints, the two flags are from the IOTLB Invalidation descriptor. Per below description, the hardware that supports nested should support drain and does not require software to ask for it. So it appears no need to define them in uapi.
"Hardware implementation with Major Version 2 or higher (VER_REG), always performs required drain without software explicitly requesting a drain in IOTLB invalidation. This field is deprecated and hardware will always report it as 1 to maintain backward compatibility with software"
Make sense. Perhaps we can also remove below code in __iommu_flush_iotlb():
/* Note: set drain read/write */ #if 0 /* * This is probably to be super secure.. Looks like we can * ignore it without any impact. */ if (cap_read_drain(iommu->cap)) val |= DMA_TLB_READ_DRAIN; #endif
Best regards, baolu