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

[Tiwei Bie <tiwei.bie@intel.com>]

On Wed, May 16, 2018 at 04:41:48AM +0300, Michael S. Tsirkin wrote:
> 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?

For the host notifiers support in vhost-user, it's
everything here!

The support in libvhost-user and vhost-user-bridge
is being done in another patchset. And we are also
working on the vIOMMU support. If we really see any
new issues in the future, I'll fix them in small
patches actively.

Thank you very much!

Best regards,
Tiwei Bie

> 
> > 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