[virtio-dev] Re: [PATCH v3 0/4] Introduce aux. notifications and virtio-vhost-user

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Oct 07, 2022 at 05:56:39PM +0100, Usama Arif wrote:
> Hi,
> 
> This patch series introduces device and driver auxiliary notifications
> as a new set of virtio device resources, as well as vhost-user device
> backend that uses these resources.
> 
> Driver auxiliary notifications allow the device to send notifications
> other than configuration changes and used buffer notifications to the
> driver, these are optional and their meaning is **device-specific**.
> 
> Device auxiliary notifcations allow the driver to send notifcations
> other than available buffer notifications to the device for example
> through a device register, these are optional and their meaning is
> **device-specific**.
> 
> These resources are used in the last patch by the virtio-vhost-user
> device in order to send/receive notifications to/from the driver
> regarding activity on the vhost-user virtqueues. By standardizing
> these resources as standalone virtio device resources, other future
> devices will be able to use them as well.

Hi Michael,
Do you have time to review this? I have been too involved in
virtio-vhost-user in the past to do a truly independent review and your
VIRTIO + vhost expertise would be perfect here.

Thanks,
Stefan

> 
> The last patch introduces the vhost-user device backend which facilitates
> vhost-user device emulation through vhost-user protocol exchanges and
> access to shared memory. Software-defined networking, storage, and other
> I/O appliances can provide services through this device.
> 
> This device is based on Wei Wang's vhost-pci work. The virtio-vhost-user
> device differs from vhost-pci because it is a single virtio
> device type that exposes the vhost-user protocol instead of a family of
> new virtio device types, one for each vhost-user device type.
> 
> A HTML version with the changes is available at [1].
> 
> For more information about virtio-vhost-user, see [2].
> 
> These patches are based on the work initially done by Stefan Hajnoczi [2]
> and continued by Nikos Dragazis [3], [4].
> 
> A working prototype implementing this spec can be reproduced using
> instructions in [5] utilizing QEMU [6] and DPDK [7].
> This is also based on the work initially done by Stefan
> and continued later by Nikos. The prototype code uses the terms
> "doorbell"/"device-specific notification" and "master"/"slave" instead of
> "device auxiliary notification"/"driver auxiliary notification" and
> "frontend"/"backend". This is based on older work, however, their
> functionality is the same. If these virtio-spec changes get approved,
> I will refractor the patches for QEMU/DPDK and send them for review
> according to the final patches in the respective mailing list.
> 
> Thanks and looking forward to your response!
> Usama
> 
> [1] https://uarif1.github.io/vvu/v3/virtio-v1.2-cs01
> [2] https://wiki.qemu.org/Features/VirtioVhostUser
> [3] https://ndragazis.github.io/dpdk-vhost-vvu-demo.html
> [4] https://lists.oasis-open.org/archives/virtio-dev/202005/msg00132.html
> [5] https://uarif1.github.io/vvu/dpdk-vvu-instructions
> [6] https://github.com/uarif1/qemu/tree/vvu
> [7] https://github.com/uarif1/dpdk/tree/vvu
> ----------
> v2->v3:
> Mostly addressing comments made by Michael S. Tsirkin:
> - Give a clearer relation between backend driver, backend device and frontend at
>   beginning of the Vhost-user Device Backend section.
> - change uuid to id.
> - Add information about inflight memory.
> 
> v1->v2:
> - Shortened device aux. notification section
> - Make data width of device aux. notifications device specific and not
>   limited to 2 bytes.
> - Added information about the minimum number of MSIX vectors.
> - Split virtio-mmio implementation of driver aux. notifications into 2
>   registers, DeviceAuxNotificationIndex and DeviceAuxNotificationData.
> - Made the shared memory section in virtio vhost-user clearer and added
>   the shared memory would look like when
>   VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS has been negotiated.
> 
> Usama Arif (4):
>   content: Introduce driver/device auxiliary notifications
>   content: Introduce driver/device aux. notification cfg type for PCI
>   content: Introduce driver/device auxiliary notifications for MMIO
>   vhost-user: add vhost-user device type
> 
>  conformance.tex       |  29 +++-
>  content.tex           | 254 +++++++++++++++++++++++++++++-----
>  introduction.tex      |   3 +
>  virtio-vhost-user.tex | 309 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 554 insertions(+), 41 deletions(-)
>  create mode 100644 virtio-vhost-user.tex
> 
> -- 
> 2.25.1
> 

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