Documentation/x86/sva.rst

1 .. SPDX-License-Identifier: GPL-2.0
19 application page-faults. For more information please refer to the PCIe
25 mmu_notifier() support to keep the device TLB cache and the CPU cache in
34 Unlike Single Root I/O Virtualization (SR-IOV), Scalable IOV (SIOV) permits
40 ID (PASID), which is a 20-bit number defined by the PCIe SIG.
43 IOMMU to track I/O on a per-PASID granularity in addition to using the PCIe
55 ENQCMD works with non-posted semantics and carries a status back if the
67 A new thread-scoped MSR (IA32_PASID) provides the connection between
69 accesses an SVA-capable device, this MSR is initialized with a newly
70 allocated PASID. The driver for the device calls an IOMMU-specific API
71 that sets up the routing for DMA and page-requests.
76 - Allocate the PASID, and program the process page-table (%cr3 register) in the
78 - Register for mmu_notifier() to track any page-table invalidations to keep
79   the device TLB in sync. For example, when a page-table entry is invalidated,
80   the IOMMU propagates the invalidation to the device TLB. This will force any
96 ENQCMD instruction, the PASID field in the descriptor is auto-filled with the
129    one or more mmap()'d portals.
134  * The single process-wide PASID is used by all threads to interact
136    thread or each thread<->device pair.
151 A Process Address Space ID (PASID) is a PCIe-defined Transaction Layer Packet
152 (TLP) prefix. A PASID is a 20-bit number allocated and managed by the OS.
160 Each doorbell is required to be spaced 4k (or page-size) apart for process
186 * Is this the same as SR-IOV?
188 Single Root I/O Virtualization (SR-IOV) focuses on providing independent
191 BARs, space for interrupts via MSI-X, its own register layout.
200 demand. SR-IOV creation and management is very static in nature. Consult
205 Creating PCIe SR-IOV type Virtual Functions (VF) is expensive. VFs require
206 duplicated hardware for PCI config space and interrupts such as MSI-X.
211 creates a software-defined device where all the configuration and control
229 Device TLB support - Device requests the IOMMU to lookup an address before
239 IOMMU works with the OS in managing consistency of page-tables with the
241 device TLB entry that might have been cached before removing the mappings from
247 VT-D:
248 https://01.org/blogs/ashokraj/2018/recent-enhancements-intel-virtualization-technology-directed-i/o…
251 https://01.org/blogs/2019/assignable-interfaces-intel-scalable-i/o-virtualization-linux
254 …intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-re…
257 https://software.intel.com/sites/default/files/341204-intel-data-streaming-accelerator-spec.pdf