This series introduces a framework, which can be used to implement
vDPA Devices in a userspace program. To implement it, the work
consist of two parts: control path emulating and data path offloading.
In the control path, the VDUSE driver will make use of message
mechnism to forward the actions (get/set features, get/st status,
get/set config space and set virtqueue states) from virtio-vdpa
driver to userspace. Userspace can use read()/write() to
receive/reply to those control messages.
In the data path, the VDUSE driver implements a MMU-based
on-chip IOMMU driver which supports both direct mapping and
indirect mapping with bounce buffer. Then userspace can access
those iova space via mmap(). Besides, eventfd mechnism is used to
trigger interrupts and forward virtqueue kicks.
The details and our user case is shown below:
------------------------ -----------------------------------------------------------
| APP | | QEMU |
| --------- | | -------------------- -------------------+<-->+------ |
| |dev/vdx| | | | device emulation | | virtio dataplane | | BDS | |
------------+----------- -----------+-----------------------+-----------------+-----
| | | |
| | emulating | offloading |
------------+---------------------------+-----------------------+-----------------+------
| | block device | | vduse driver | | vdpa device | | TCP/IP | |
| -------+-------- --------+-------- +------+------- -----+---- |
| | | | | | |
| | | | | | |
| ----------+---------- ----------+----------- | | | |
| | virtio-blk driver | | virtio-vdpa driver | | | | |
| ----------+---------- ----------+----------- | | | |
| | | | | | |
| | ------------------ | | |
| ----------------------------------------------------- ---+--- |
------------------------------------------------------------------------------ | NIC |---
---+---
|
---------+---------
| Remote Storages |
-------------------
We make use of it to implement a block device connecting to
our distributed storage, which can be used in containers and
bare metal. Compared with qemu-nbd solution, this solution has
higher performance, and we can have an unified technology stack
in VM and containers for remote storages.
To test it with a host disk (e.g. /dev/sdx):
$ qemu-storage-daemon \
--chardev socket,id=charmonitor,path=/tmp/qmp.sock,server,nowait \
--monitor chardev=charmonitor \
--blockdev driver=host_device,cache.direct=on,aio=native,filename=/dev/sdx,node-name=disk0 \
--export vduse-blk,id=test,node-name=disk0,writable=on,vduse-id=1,num-queues=16,queue-size=128
The qemu-storage-daemon can be found at https://github.com/bytedance/qemu/tree/vduse
Future work:
- Improve performance (e.g. zero copy implementation in datapath)
- Config interrupt support
- Userspace library (find a way to reuse device emulation code in qemu/rust-vmm)
Xie Yongji (4):
mm: export zap_page_range() for driver use
vduse: Introduce VDUSE - vDPA Device in Userspace
vduse: grab the module's references until there is no vduse device
vduse: Add memory shrinker to reclaim bounce pages
drivers/vdpa/Kconfig | 8 +
drivers/vdpa/Makefile | 1 +
drivers/vdpa/vdpa_user/Makefile | 5 +
drivers/vdpa/vdpa_user/eventfd.c | 221 ++++++
drivers/vdpa/vdpa_user/eventfd.h | 48 ++
drivers/vdpa/vdpa_user/iova_domain.c | 488 ++++++++++++
drivers/vdpa/vdpa_user/iova_domain.h | 104 +++
drivers/vdpa/vdpa_user/vduse.h | 66 ++
drivers/vdpa/vdpa_user/vduse_dev.c | 1081 ++++++++++++++++++++++++++
include/uapi/linux/vduse.h | 85 ++
mm/memory.c | 1 +
11 files changed, 2108 insertions(+)
create mode 100644 drivers/vdpa/vdpa_user/Makefile
create mode 100644 drivers/vdpa/vdpa_user/eventfd.c
create mode 100644 drivers/vdpa/vdpa_user/eventfd.h
create mode 100644 drivers/vdpa/vdpa_user/iova_domain.c
create mode 100644 drivers/vdpa/vdpa_user/iova_domain.h
create mode 100644 drivers/vdpa/vdpa_user/vduse.h
create mode 100644 drivers/vdpa/vdpa_user/vduse_dev.c
create mode 100644 include/uapi/linux/vduse.h
--
2.25.1
