Re: [PATCH v2 06/19] iommufd/viommu: Add IOMMU_VIOMMU_SET/UNSET_VDEV_ID ioctl

On Fri, Oct 04, 2024 at 11:13:46AM -0700, Nicolin Chen wrote:

On Fri, Oct 04, 2024 at 08:41:47AM -0300, Jason Gunthorpe wrote:

quoted

On Fri, Oct 04, 2024 at 02:32:28PM +1000, Alexey Kardashevskiy wrote:

quoted

For my SEV-TIO exercise ("trusted IO"), I am looking for a kernel interface
to pass the guest's BDFs for a specific host device (which is passed
through) and nothing in the kernel has any knowledge of it atm, is this the
right place, or another ioctl() is needed here?

We probably need to add the vRID as well to this struct for that
reason.

"vRID"/"vBDF" doesn't sound very generic to me to put in this
structure, though PCI devices are and very likely will be the
only users of this Virtual Device for a while. Any good idea?

It isn't necessarily bad to have a pci field as long as we can
somehow understand when it is used.

Also, I am wondering if the uAPI structure of Virtual Device
should have a driver-specific data structure. And the vdev_id
should be in the driver-specific struct. So, it could stay in
corresponding naming, "Stream ID", "Device ID" or "Context ID"
v.s. a generic "Virtual ID" in the top-level structure? Then,
other info like CCA can be put in the driver-level structure
of SMMU's.

I'd to avoid a iommu-driver specific structure here, but I fear we
will have a "lowervisor" (sigh) specific structure for the widely
varied CC/pkvm/etc world.

Agreed. That also implies that a vRID is quite independent to
the IOMMU right? So, I think that the reason of adding a vRID
to the virtual deivce uAPI/structure should be IOMMU requiring
it?

I would like to use this API to link in the CC/pkvm/etc world, and use
it to create not just the vIOMMU components but link up to the
"lowervisor" components as well, since it is all the same stuff
basically.

Jason