On 2021-05-17 16:35, Joerg Roedel wrote:
On Mon, May 17, 2021 at 10:35:00AM -0300, Jason Gunthorpe wrote:
Well, I'm sorry, but there is a huge other thread talking about the
IOASID design in great detail and why this is all needed. Jumping into
this thread without context and basically rejecting all the
conclusions that were reached over the last several weeks is really
not helpful - especially since your objection is not technical.
I think you should wait for Intel to put together the /dev/ioasid uAPI
proposal and the example use cases it should address then you can give
feedback there, with proper context.
Yes, I think the next step is that someone who read the whole thread
writes up the conclusions and a rough /dev/ioasid API proposal, also
mentioning the use-cases it addresses. Based on that we can discuss the
implications this needs to have for IOMMU-API and code.
From the use-cases I know the mdev concept is just fine. But if there is
a more generic one we can talk about it.
Just to add another voice here, I have some colleagues working on
drivers where they want to use SMMU Substream IDs for a single hardware
block to operate on multiple iommu_domains managed entirely within the
kernel. Using an mdev-like approach with aux domains is pretty much the
ideal fit for this use-case, while all the IOASID discussion appears
centred on SVA and userspace interfaces, and as such barely relevant if
at all.
I seem to recall a non-trivial amount of effort going into the aux
domain design too, so the promise of replacing it with "a big TBD" just
because vfio-mdev turned out to be awful hardly fills me with enthusiasm
either :/
Robin.
