> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx> > Sent: Thursday, June 8, 2023 4:08 PM > > 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 This seems dead code. But it is there for a long time since below commit. ba39592764ed20cee09aae5352e603a27bf56b0d Regards, Yi Liu
