Re: [Qemu-devel] [PATCH v3 0/6] Extend vhost-user to support registering external host notifiers

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

On Thu, Apr 12, 2018 at 11:12:26PM +0800, Tiwei Bie wrote:
> The original subject is: Extend vhost-user to support VFIO based accelerators
> 
> Update notes
> ============
> 
> Now, this patch set just focuses on adding the support for
> registering memory region based host notifiers. With this
> support, guest driver in the VM will be able to notify the
> hardware device at the vhost backend directly.
> 
> It's one of the most important things in vDPA -- the host
> notification offload. Because, normally, the hardware device
> heavily depends on the notifications. Without this support,
> there will be a lot of VM-Exit happen due to the notifications
> from guest driver (it will drop the VM performance) and a
> lot of CPU resources wasted to do the notification relay
> (it will make the hardware offload less attractive, because
> one important goal of hardware offload is to free the CPU
> resources).
> 
> More backgrounds of this patch set can be found from the
> cover letter of the previous versions:
> 
> RFC: http://lists.nongnu.org/archive/html/qemu-devel/2017-12/msg04844.html
> v1:  http://lists.nongnu.org/archive/html/qemu-devel/2018-01/msg06028.html
> v2:  http://lists.nongnu.org/archive/html/qemu-devel/2018-03/msg05009.html

So I don't think there are any outstanding issues here.
Did I miss anything?

> v2 -> v3:
> - A better implementation of the shared vhost-user state (MST);
> - Use bus callback to add/delete subregions for notification (MST);
> - Refine APIs' names which add/delete subregions for notification (MST);
> - Refine the doc of the new vhost-user types and messages (MST);
> - Separate host notification offload from the guest notification offload (MST);
> - Drop the guest notification offload support from this patch;
> - Add memory filter for vhost backend to filter the sections they can handle;
> 
> v1 -> v2:
> - Add some explanations about why extend vhost-user in commit log (Paolo);
> - Bug fix in slave_read() according to Stefan's fix in DPDK;
> - Remove IOMMU feature check and related commit log;
> - Some minor refinements;
> - Rebase to the latest QEMU;
> 
> RFC -> v1:
> - Add some details about how vDPA works in cover letter (Alexey)
> - Add some details about the OVS offload use-case in cover letter (Jason)
> - Move PCI specific stuffs out of vhost-user (Jason)
> - Handle the virtual IOMMU case (Jason)
> - Move VFIO group management code into vfio/common.c (Alex)
> - Various refinements;
> (approximately sorted by comment posting time)
> 
> Tiwei Bie (6):
>   vhost-user: add Net prefix to internal state structure
>   vhost-user: introduce shared vhost-user state
>   vhost-user: support receiving file descriptors in slave_read
>   virtio: support setting memory region based host notifier
>   vhost: allow backends to filter memory sections
>   vhost-user: support registering external host notifiers
> 
>  backends/cryptodev-vhost-user.c     |  20 +++-
>  docs/interop/vhost-user.txt         |  33 ++++++
>  hw/block/vhost-user-blk.c           |  22 +++-
>  hw/scsi/vhost-user-scsi.c           |  20 +++-
>  hw/virtio/Makefile.objs             |   2 +-
>  hw/virtio/vhost-stub.c              |  10 ++
>  hw/virtio/vhost-user.c              | 206 ++++++++++++++++++++++++++++++++++--
>  hw/virtio/vhost.c                   |   9 +-
>  hw/virtio/virtio-pci.c              |  22 ++++
>  hw/virtio/virtio.c                  |  13 +++
>  include/hw/virtio/vhost-backend.h   |   4 +
>  include/hw/virtio/vhost-user-blk.h  |   2 +
>  include/hw/virtio/vhost-user-scsi.h |   2 +
>  include/hw/virtio/vhost-user.h      |  28 +++++
>  include/hw/virtio/virtio-bus.h      |   2 +
>  include/hw/virtio/virtio.h          |   2 +
>  net/vhost-user.c                    |  78 +++++++++-----
>  17 files changed, 433 insertions(+), 42 deletions(-)
>  create mode 100644 include/hw/virtio/vhost-user.h
> 
> -- 
> 2.11.0