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Message-ID: <20210414032909-mutt-send-email-mst@kernel.org>
Date: Wed, 14 Apr 2021 03:34:16 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Xie Yongji <xieyongji@...edance.com>
Cc: jasowang@...hat.com, stefanha@...hat.com, sgarzare@...hat.com,
parav@...dia.com, hch@...radead.org,
christian.brauner@...onical.com, rdunlap@...radead.org,
willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
bcrl@...ck.org, corbet@....net, mika.penttila@...tfour.com,
dan.carpenter@...cle.com,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 00/10] Introduce VDUSE - vDPA Device in Userspace
On Wed, Mar 31, 2021 at 04:05:09PM +0800, 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. 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 |
> -------------------
This all looks quite similar to vhost-user-block except that one
does not need any kernel support at all.
So I am still scratching my head about its advantages over
vhost-user-block.
> 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.
Maybe the container part is the answer. How does that stack look?
> 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 type=vduse-blk,id=test,node-name=disk0,writable=on,name=vduse-null,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
> - Userspace library (find a way to reuse device emulation code in qemu/rust-vmm)
>
> V5 to V6:
> - Export receive_fd() instead of __receive_fd()
> - Factor out the unmapping logic of pa and va separatedly
> - Remove the logic of bounce page allocation in page fault handler
> - Use PAGE_SIZE as IOVA allocation granule
> - Add EPOLLOUT support
> - Enable setting API version in userspace
> - Fix some bugs
>
> V4 to V5:
> - Remove the patch for irq binding
> - Use a single IOTLB for all types of mapping
> - Factor out vhost_vdpa_pa_map()
> - Add some sample codes in document
> - Use receice_fd_user() to pass file descriptor
> - Fix some bugs
>
> V3 to V4:
> - Rebase to vhost.git
> - Split some patches
> - Add some documents
> - Use ioctl to inject interrupt rather than eventfd
> - Enable config interrupt support
> - Support binding irq to the specified cpu
> - Add two module parameter to limit bounce/iova size
> - Create char device rather than anon inode per vduse
> - Reuse vhost IOTLB for iova domain
> - Rework the message mechnism in control path
>
> V2 to V3:
> - Rework the MMU-based IOMMU driver
> - Use the iova domain as iova allocator instead of genpool
> - Support transferring vma->vm_file in vhost-vdpa
> - Add SVA support in vhost-vdpa
> - Remove the patches on bounce pages reclaim
>
> V1 to V2:
> - Add vhost-vdpa support
> - 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 (10):
> file: Export receive_fd() to modules
> eventfd: Increase the recursion depth of eventfd_signal()
> vhost-vdpa: protect concurrent access to vhost device iotlb
> vhost-iotlb: Add an opaque pointer for vhost IOTLB
> vdpa: Add an opaque pointer for vdpa_config_ops.dma_map()
> vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap()
> vdpa: Support transferring virtual addressing during DMA mapping
> vduse: Implement an MMU-based IOMMU driver
> vduse: Introduce VDUSE - vDPA Device in Userspace
> Documentation: Add documentation for VDUSE
>
> Documentation/userspace-api/index.rst | 1 +
> Documentation/userspace-api/ioctl/ioctl-number.rst | 1 +
> Documentation/userspace-api/vduse.rst | 212 +++
> drivers/vdpa/Kconfig | 10 +
> drivers/vdpa/Makefile | 1 +
> drivers/vdpa/ifcvf/ifcvf_main.c | 2 +-
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
> drivers/vdpa/vdpa.c | 9 +-
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 8 +-
> drivers/vdpa/vdpa_user/Makefile | 5 +
> drivers/vdpa/vdpa_user/iova_domain.c | 521 ++++++++
> drivers/vdpa/vdpa_user/iova_domain.h | 70 +
> drivers/vdpa/vdpa_user/vduse_dev.c | 1362 ++++++++++++++++++++
> drivers/vdpa/virtio_pci/vp_vdpa.c | 2 +-
> drivers/vhost/iotlb.c | 20 +-
> drivers/vhost/vdpa.c | 154 ++-
> fs/eventfd.c | 2 +-
> fs/file.c | 6 +
> include/linux/eventfd.h | 5 +-
> include/linux/file.h | 7 +-
> include/linux/vdpa.h | 21 +-
> include/linux/vhost_iotlb.h | 3 +
> include/uapi/linux/vduse.h | 175 +++
> 23 files changed, 2548 insertions(+), 51 deletions(-)
> create mode 100644 Documentation/userspace-api/vduse.rst
> create mode 100644 drivers/vdpa/vdpa_user/Makefile
> 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_dev.c
> create mode 100644 include/uapi/linux/vduse.h
>
> --
> 2.11.0
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