Hi Jason, On Fri, 7 May 2021 16:28:10 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > The unanswered question is how do we plumb from vIOMMU without a custom > > allocator to get a system wide PASID? > > PASID allocation is part of the iommu driver, it really shouldn't be > global. > In the current code, the pluggable custom allocator *is* part of the iommu vendor driver. If it decides the allocation is global then it should be suitable for the platform since there will never be a VT-d IOMMU on another vendor's platform. It is true that the default allocator is global which suites the current needs. I am just wondering if we are solving a problem does not exist yet. > When the architecture code goes to allocate a single PASID for the > mm_struct it should flag that allocation request with a 'must work for > all RIDs flag' and the iommu driver should take care of it. That might > mean the iommu driver consults a global static xarray, or maybe it > does a hypercall, but it should be done through that API, not a side > care global singleton. Why do we need to flag the allocation every time if on a platform *every* PASID can potentially be global? At the time of allocation, we don't know if the PASID will be used for a shared (ENQCMD) or a dedicated workqueue. Thanks, Jacob
