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Subject[PATCH V4 0/5] vDPA support
Hi all:

This is an update version of vDPA support in kernel.

vDPA device is a device that uses a datapath which complies with the
virtio specifications with vendor specific control path. vDPA devices
can be both physically located on the hardware or emulated by
software. vDPA hardware devices are usually implemented through PCIE
with the following types:

- PF (Physical Function) - A single Physical Function
- VF (Virtual Function) - Device that supports single root I/O
virtualization (SR-IOV). Its Virtual Function (VF) represents a
virtualized instance of the device that can be assigned to different
- ADI (Assignable Device Interface) and its equivalents - With
technologies such as Intel Scalable IOV, a virtual device (VDEV)
composed by host OS utilizing one or more ADIs. Or its equivalent
like SF (Sub function) from Mellanox.

From a driver's perspective, depends on how and where the DMA
translation is done, vDPA devices are split into two types:

- Platform specific DMA translation - From the driver's perspective,
the device can be used on a platform where device access to data in
memory is limited and/or translated. An example is a PCIE vDPA whose
DMA request was tagged via a bus (e.g PCIE) specific way. DMA
translation and protection are done at PCIE bus IOMMU level.
- Device specific DMA translation - The device implements DMA
isolation and protection through its own logic. An example is a vDPA
device which uses on-chip IOMMU.

To hide the differences and complexity of the above types for a vDPA
device/IOMMU options and in order to present a generic virtio device
to the upper layer, a device agnostic framework is required.

This series introduces a software vDPA bus which abstracts the
common attributes of vDPA device, vDPA bus driver and the
communication method, the bus operations (vdpa_config_ops) between the
vDPA device abstraction and the vDPA bus driver. This allows multiple
types of drivers to be used for vDPA device like the virtio_vdpa and
vhost_vdpa driver to operate on the bus and allow vDPA device could be
used by either kernel virtio driver or userspace vhost drivers as:

virtio drivers vhost drivers
| |
[virtio bus] [vhost uAPI]
| |
virtio device vhost device
virtio_vdpa drv vhost_vdpa drv
\ /
[vDPA bus]
vDPA device
hardware drv
[hardware bus]
vDPA hardware

virtio_vdpa driver is a transport implementation for kernel virtio
drivers on top of vDPA bus operations. An alternative is to refactor
virtio bus which is sub-optimal since the bus and drivers are designed
to be use by kernel subsystem, a non-trivial major refactoring is
needed which may impact a brunches of drivers and devices
implementation inside the kernel. Using a new transport may grealy
simply both the design and changes.

vhost_vdpa driver is a new type of vhost device which allows userspace
vhost drivers to use vDPA devices via vhost uAPI (with minor
extension). This help to minimize the changes of existed vhost drivers
for using vDPA devices.

With the abstraction of vDPA bus and vDPA bus operations, the
difference and complexity of the under layer hardware is hidden from
upper layer. The vDPA bus drivers on top can use a unified
vdpa_config_ops to control different types of vDPA device.

This series contains the bus and virtio_vdpa implementation. We are
working on the vhost part and IFCVF (vDPA driver from Intel) which
will be posted in future few days.


Changes from V3:

- various Kconfig fixes (Randy)

Changes from V2:

- release idr in the release function for put_device() unwind (Jason)
- don't panic when fail to register vdpa bus (Jason)
- use unsigned int instead of int for ida (Jason)
- fix the wrong commit log in virito_vdpa patches (Jason)
- make vdpa_sim depends on RUNTIME_TESTING_MENU (Michael)
- provide a bus release function for vDPA device (Jason)
- fix the wrong unwind when creating devices for vDPA simulator (Jason)
- move vDPA simulator to a dedicated directory (Lingshan)
- cancel the work before release vDPA simulator

Changes from V1:

- drop sysfs API, leave the management interface to future development
- introduce incremental DMA ops (dma_map/dma_unmap) (Michael)
- introduce dma_device and use it instead of parent device for doing
IOMMU or DMA from bus driver (Michael, Jason, Ling Shan, Tiwei)
- accept parent device and dma device when register vdpa device
- coding style and compile fixes (Randy)
- using vdpa_xxx instead of xxx_vdpa (Jason)
- ove vDPA accessors to header and make it static inline (Jason)
- split vdp_register_device() into two helpers vdpa_init_device() and
vdpa_register_device() which allows intermediate step to be done (Jason)
- warn on invalidate queue state when fail to creating virtqueue (Jason)
- make to_virtio_vdpa_device() static (Jason)
- use kmalloc/kfree instead of devres for virtio vdpa device (Jason)
- avoid using cast in vdpa bus function (Jason)
- introduce module_vdpa_driver and fix module refcnt (Jason)
- fix returning freed address in vdapsim coherent DMA addr allocation (Dan)
- various other fixes and tweaks


Jason Wang (5):
vhost: factor out IOTLB
vringh: IOTLB support
vDPA: introduce vDPA bus
virtio: introduce a vDPA based transport
vdpasim: vDPA device simulator

drivers/vhost/Kconfig | 6 +
drivers/vhost/Kconfig.vringh | 1 +
drivers/vhost/Makefile | 2 +
drivers/vhost/net.c | 2 +-
drivers/vhost/vhost.c | 221 +++-----
drivers/vhost/vhost.h | 36 +-
drivers/vhost/vhost_iotlb.c | 171 ++++++
drivers/vhost/vringh.c | 421 ++++++++++++++-
drivers/virtio/Kconfig | 15 +
drivers/virtio/Makefile | 2 +
drivers/virtio/vdpa/Kconfig | 26 +
drivers/virtio/vdpa/Makefile | 3 +
drivers/virtio/vdpa/vdpa.c | 167 ++++++
drivers/virtio/vdpa/vdpa_sim/Makefile | 2 +
drivers/virtio/vdpa/vdpa_sim/vdpa_sim.c | 660 ++++++++++++++++++++++++
drivers/virtio/virtio_vdpa.c | 392 ++++++++++++++
include/linux/vdpa.h | 232 +++++++++
include/linux/vhost_iotlb.h | 45 ++
include/linux/vringh.h | 36 ++
20 files changed, 2238 insertions(+), 204 deletions(-)
create mode 100644 drivers/vhost/vhost_iotlb.c
create mode 100644 drivers/virtio/vdpa/Kconfig
create mode 100644 drivers/virtio/vdpa/Makefile
create mode 100644 drivers/virtio/vdpa/vdpa.c
create mode 100644 drivers/virtio/vdpa/vdpa_sim/Makefile
create mode 100644 drivers/virtio/vdpa/vdpa_sim/vdpa_sim.c
create mode 100644 drivers/virtio/virtio_vdpa.c
create mode 100644 include/linux/vdpa.h
create mode 100644 include/linux/vhost_iotlb.h


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