On Thu, Mar 20, 2025 at 03:57:26PM -0300, Jason Gunthorpe wrote: > On Thu, Mar 20, 2025 at 09:47:32AM -0700, Nicolin Chen wrote: > > > In that regard, honestly, I don't quite get this out_capabilities. > > Yeah, I think it is best thought of as place to put discoverability if > people want discoverability. > > I have had a wait and see feeling in this area since I don't know what > qemu or libvirt would actually use. Both ARM and Intel have max_pasid_log2 being reported somewhere in their vendor data structures. So, unless user space really wants that info immediately without involving the vendor IOMMU, this max_pasid_log2 seems to be redundant. Also, this patch polls two IOMMU caps out of pci_pasid_status() that is a per device function. Is this okay? Can it end up with two devices (one has PASID; the other doesn't) behind the same IOMMU reporting two different sets of out_capabilities, which were supposed to be the same since it the same IOMMU HW? Thanks Nicolin
