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

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Oct 27, 2022 at 03:54:41PM -0400, Stefan Hajnoczi wrote:
> 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


Plan to, just trying to merge a ton of stuff before qemu freeze.

> > 
> > 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
> >