On Wed, Sep 22, 2021 at 03:40:25AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe <[email protected]> > > Sent: Wednesday, September 22, 2021 1:45 AM > > > > On Sun, Sep 19, 2021 at 02:38:39PM +0800, Liu Yi L wrote: > > > This patch adds IOASID allocation/free interface per iommufd. When > > > allocating an IOASID, userspace is expected to specify the type and > > > format information for the target I/O page table. > > > > > > This RFC supports only one type (IOMMU_IOASID_TYPE_KERNEL_TYPE1V2), > > > implying a kernel-managed I/O page table with vfio type1v2 mapping > > > semantics. For this type the user should specify the addr_width of > > > the I/O address space and whether the I/O page table is created in > > > an iommu enfore_snoop format. enforce_snoop must be true at this point, > > > as the false setting requires additional contract with KVM on handling > > > WBINVD emulation, which can be added later. > > > > > > Userspace is expected to call IOMMU_CHECK_EXTENSION (see next patch) > > > for what formats can be specified when allocating an IOASID. > > > > > > Open: > > > - Devices on PPC platform currently use a different iommu driver in vfio. > > > Per previous discussion they can also use vfio type1v2 as long as there > > > is a way to claim a specific iova range from a system-wide address > > > space. > > > This requirement doesn't sound PPC specific, as addr_width for pci > > devices > > > can be also represented by a range [0, 2^addr_width-1]. This RFC hasn't > > > adopted this design yet. We hope to have formal alignment in v1 > > discussion > > > and then decide how to incorporate it in v2. > > > > I think the request was to include a start/end IO address hint when > > creating the ios. When the kernel creates it then it can return the > > is the hint single-range or could be multiple-ranges? > > > actual geometry including any holes via a query. > > I'd like to see a detail flow from David on how the uAPI works today with > existing spapr driver and what exact changes he'd like to make on this > proposed interface. Above info is still insufficient for us to think about the > right solution. > > > > > > - Currently ioasid term has already been used in the kernel > > (drivers/iommu/ > > > ioasid.c) to represent the hardware I/O address space ID in the wire. It > > > covers both PCI PASID (Process Address Space ID) and ARM SSID (Sub- > > Stream > > > ID). We need find a way to resolve the naming conflict between the > > hardware > > > ID and software handle. One option is to rename the existing ioasid to > > > be > > > pasid or ssid, given their full names still sound generic. Appreciate > > > more > > > thoughts on this open! > > > > ioas works well here I think. Use ioas_id to refer to the xarray > > index. > > What about when introducing pasid to this uAPI? Then use ioas_id > for the xarray index and ioasid to represent pasid/ssid?
This is probably obsoleted by Jason's other comments, but definitely
don't use "ioas_id" and "ioasid" to mean different things. Having
meaningfully different things distinguished only by an underscore is
not a good idea.
> At this point
> the software handle and hardware id are mixed together thus need
> a clear terminology to differentiate them.
>
>
> Thanks
> Kevin
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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