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Date: Wed, 23 Dec 2020 14:38:35 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xie Yongji <xieyongji@...edance.com>, mst@...hat.com,
stefanha@...hat.com, sgarzare@...hat.com, parav@...dia.com,
akpm@...ux-foundation.org, rdunlap@...radead.org,
willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
bcrl@...ck.org, corbet@....net
Cc: virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
kvm@...r.kernel.org, linux-aio@...ck.org,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC v2 00/13] Introduce VDUSE - vDPA Device in Userspace
On 2020/12/22 下午10:52, Xie Yongji wrote:
> This series introduces a framework, which can be used to implement
> vDPA Devices in a userspace program. The work consist of two parts:
> control path forwarding and data path offloading.
>
> In the control path, the VDUSE driver will make use of message
> mechnism to forward the config operation from vdpa bus driver
> to userspace. Userspace can use read()/write() to receive/reply
> those control messages.
>
> In the data path, the core is mapping dma buffer into VDUSE
> daemon's address space, which can be implemented in different ways
> depending on the vdpa bus to which the vDPA device is attached.
>
> In virtio-vdpa case, we implements a MMU-based on-chip IOMMU driver with
> bounce-buffering mechanism to achieve that.
Rethink about the bounce buffer stuffs. I wonder instead of using kernel
pages with mmap(), how about just use userspace pages like what vhost did?
It means we need a worker to do bouncing but we don't need to care about
annoying stuffs like page reclaiming?
> And in vhost-vdpa case, the dma
> buffer is reside in a userspace memory region which can be shared to the
> VDUSE userspace processs via transferring the shmfd.
>
> The details and our user case is shown below:
>
> ------------------------ ------------------------- ----------------------------------------------
> | Container | | QEMU(VM) | | VDUSE daemon |
> | --------- | | ------------------- | | ------------------------- ---------------- |
> | |dev/vdx| | | |/dev/vhost-vdpa-x| | | | vDPA device emulation | | block driver | |
> ------------+----------- -----------+------------ -------------+----------------------+---------
> | | | |
> | | | |
> ------------+---------------------------+----------------------------+----------------------+---------
> | | block device | | vhost device | | vduse driver | | TCP/IP | |
> | -------+-------- --------+-------- -------+-------- -----+---- |
> | | | | | |
> | ----------+---------- ----------+----------- -------+------- | |
> | | virtio-blk driver | | vhost-vdpa driver | | vdpa device | | |
> | ----------+---------- ----------+----------- -------+------- | |
> | | virtio bus | | | |
> | --------+----+----------- | | | |
> | | | | | |
> | ----------+---------- | | | |
> | | virtio-blk device | | | | |
> | ----------+---------- | | | |
> | | | | | |
> | -----------+----------- | | | |
> | | virtio-vdpa driver | | | | |
> | -----------+----------- | | | |
> | | | | vdpa bus | |
> | -----------+----------------------+---------------------------+------------ | |
> | ---+--- |
> -----------------------------------------------------------------------------------------| NIC |------
> ---+---
> |
> ---------+---------
> | Remote Storages |
> -------------------
>
> We make use of it to implement a block device connecting to
> our distributed storage, which can be used both in containers and
> VMs. Thus, we can have an unified technology stack in this two cases.
>
> To test it with null-blk:
>
> $ 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/nullb0,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)
>
> This is now based on below series:
> https://lore.kernel.org/netdev/20201112064005.349268-1-parav@nvidia.com/
>
> V1 to V2:
> - Add vhost-vdpa support
I may miss something but I don't see any code to support that. E.g
neither set_map nor dma_map/unmap is implemented in the config ops.
Thanks
> - Add some documents
> - Based on the vdpa management tool
> - Introduce a workqueue for irq injection
> - Replace interval tree with array map to store the iova_map
>
> Xie Yongji (13):
> mm: export zap_page_range() for driver use
> eventfd: track eventfd_signal() recursion depth separately in different cases
> eventfd: Increase the recursion depth of eventfd_signal()
> vdpa: Remove the restriction that only supports virtio-net devices
> vdpa: Pass the netlink attributes to ops.dev_add()
> vduse: Introduce VDUSE - vDPA Device in Userspace
> vduse: support get/set virtqueue state
> vdpa: Introduce process_iotlb_msg() in vdpa_config_ops
> vduse: Add support for processing vhost iotlb message
> vduse: grab the module's references until there is no vduse device
> vduse/iova_domain: Support reclaiming bounce pages
> vduse: Add memory shrinker to reclaim bounce pages
> vduse: Introduce a workqueue for irq injection
>
> Documentation/driver-api/vduse.rst | 91 ++
> Documentation/userspace-api/ioctl/ioctl-number.rst | 1 +
> drivers/vdpa/Kconfig | 8 +
> drivers/vdpa/Makefile | 1 +
> drivers/vdpa/vdpa.c | 2 +-
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 +-
> drivers/vdpa/vdpa_user/Makefile | 5 +
> drivers/vdpa/vdpa_user/eventfd.c | 229 ++++
> drivers/vdpa/vdpa_user/eventfd.h | 48 +
> drivers/vdpa/vdpa_user/iova_domain.c | 517 ++++++++
> drivers/vdpa/vdpa_user/iova_domain.h | 103 ++
> drivers/vdpa/vdpa_user/vduse.h | 59 +
> drivers/vdpa/vdpa_user/vduse_dev.c | 1373 ++++++++++++++++++++
> drivers/vhost/vdpa.c | 34 +-
> fs/aio.c | 3 +-
> fs/eventfd.c | 20 +-
> include/linux/eventfd.h | 5 +-
> include/linux/vdpa.h | 11 +-
> include/uapi/linux/vdpa.h | 1 +
> include/uapi/linux/vduse.h | 119 ++
> mm/memory.c | 1 +
> 21 files changed, 2598 insertions(+), 36 deletions(-)
> create mode 100644 Documentation/driver-api/vduse.rst
> 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
>
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