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. Is this the reason for passing addr_width to IOASID_ALLOC? I didn't get what it's used for or why it's mandatory. But for PPC it sounds like it should be an address range instead of an upper limit? Thanks, Jean > 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. > > - 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!
