The last email was a draft sent by mistake. This is the full version. Alex Williamson <alex.williamson@xxxxxxxxxx> writes: > Currently we have a struct vfio_pci_region stored in an array that we > dynamically resize for device specific regions and the offset is > determined statically from the array index. We could easily specify an > offset and alias field on that object if we wanted to make the address > space more compact (without a maple tree) and facilitate multiple > regions referencing the same device resource. This is all just > implementation decisions. We also don't need to support read/write on > new regions, we could have them exist advertising only mmap support via > REGION_INFO, which simplifies and is consistent with the existing API. > What I understand is that you’re proposing an API to create a new region. The user would then fetch a new index and use it with REGION_INFO to obtain the pgoff. This feels like adding another layer on top of the pgoff, while the end goal remains the same. I'm not sure an alias region offers more value than simply creating an alias pgoff. It may even be more confusing, since—AFAIU—users expect indexes to align with PCI BAR indexes in the PCI case. We would also need either a new API or an additional REGION_INFO member to tell the user which index the alias refers to and what extra attributes it has. Ultimately, both approaches are very similar: one creates a full alias region, the other just a pgoff alias, but both would require nearly the same internal implementation for pgoff handling. The key question is: does a full region alias provide any tangible benefits over a pgoff alias? In my opinion, it’s clearer to simply have the user call e.g REQUEST_REGION_MMAP (which returns a pgoff for mmap) rather than request full region creation. - MNAdam Amazon Web Services Development Center Germany GmbH Tamara-Danz-Str. 13 10243 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597
