On Tue, Sep 21, 2021 at 02:44:38PM -0300, Jason Gunthorpe wrote: > 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 > actual geometry including any holes via a query.
So part of the point of specifying start/end addresses is that
explicitly querying holes shouldn't be necessary: if the requested
range crosses a hole, it should fail. If you didn't really need all
that range, you shouldn't have asked for it.
Which means these aren't really "hints" but optionally supplied
constraints.
--
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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