Re: [RFC PATCH v2 00/19] Control VQ support in vDPA

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在 2022/2/25 上午5:22, Gautam Dawar 写道:
Hi All:

This series tries to add the support for control virtqueue in vDPA.

Control virtqueue is used by networking device for accepting various
commands from the driver. It's a must to support multiqueue and other
configurations.

When used by vhost-vDPA bus driver for VM, the control virtqueue
should be shadowed via userspace VMM (Qemu) instead of being assigned
directly to Guest. This is because Qemu needs to know the device state
in order to start and stop device correctly (e.g for Live Migration).

This requies to isolate the memory mapping for control virtqueue
presented by vhost-vDPA to prevent guest from accessing it directly.

To achieve this, vDPA introduce two new abstractions:

- address space: identified through address space id (ASID) and a set
                  of memory mapping in maintained
- virtqueue group: the minimal set of virtqueues that must share an
                  address space

Device needs to advertise the following attributes to vDPA:

- the number of address spaces supported in the device
- the number of virtqueue groups supported in the device
- the mappings from a specific virtqueue to its virtqueue groups

The mappings from virtqueue to virtqueue groups is fixed and defined
by vDPA device driver. E.g:

- For the device that has hardware ASID support, it can simply
   advertise a per virtqueue virtqueue group.
- For the device that does not have hardware ASID support, it can
   simply advertise a single virtqueue group that contains all
   virtqueues. Or if it wants a software emulated control virtqueue, it
   can advertise two virtqueue groups, one is for cvq, another is for
   the rest virtqueues.

vDPA also allow to change the association between virtqueue group and
address space. So in the case of control virtqueue, userspace
VMM(Qemu) may use a dedicated address space for the control virtqueue
group to isolate the memory mapping.

The vhost/vhost-vDPA is also extend for the userspace to:

- query the number of virtqueue groups and address spaces supported by
   the device
- query the virtqueue group for a specific virtqueue
- assocaite a virtqueue group with an address space
- send ASID based IOTLB commands

This will help userspace VMM(Qemu) to detect whether the control vq
could be supported and isolate memory mappings of control virtqueue
from the others.

To demonstrate the usage, vDPA simulator is extended to support
setting MAC address via a emulated control virtqueue.

Please review.

Changes since v1:

- Rebased the v1 patch series on vhost branch of MST vhost git repo
   git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git/log/?h=vhost
- Updates to accommodate vdpa_sim changes from monolithic module in
   kernel used v1 patch series to current modularized class (net, block)
   based approach.
- Added new attributes (ngroups and nas) to "vdpasim_dev_attr" and
   propagated them from vdpa_sim_net to vdpa_sim
- Widened the data-type for "asid" member of vhost_msg_v2 to __u32
   to accommodate PASID


This is great. Then the semantic matches exactly the PASID proposal here[1].


- Fixed the buildbot warnings
- Resolved all checkpatch.pl errors and warnings
- Tested both control and datapath with Xilinx Smartnic SN1000 series
   device using QEMU implementing the Shadow virtqueue and support for
   VQ groups and ASID available at:
   github.com/eugpermar/qemu/releases/tag/vdpa_sw_live_migration.d%2F
   asid_groups-v1.d%2F00


On top, we may extend the netlink protocol to report the mapping between virtqueue to its groups.


Thanks

[1] https://www.mail-archive.com/virtio-dev@xxxxxxxxxxxxxxxxxxxx/msg08077.html



Changes since RFC:

- tweak vhost uAPI documentation
- switch to use device specific IOTLB really in patch 4
- tweak the commit log
- fix that ASID in vhost is claimed to be 32 actually but 16bit
   actually
- fix use after free when using ASID with IOTLB batching requests
- switch to use Stefano's patch for having separated iov
- remove unused "used_as" variable
- fix the iotlb/asid checking in vhost_vdpa_unmap()

Thanks

Gautam Dawar (19):
   vhost: move the backend feature bits to vhost_types.h
   virtio-vdpa: don't set callback if virtio doesn't need it
   vhost-vdpa: passing iotlb to IOMMU mapping helpers
   vhost-vdpa: switch to use vhost-vdpa specific IOTLB
   vdpa: introduce virtqueue groups
   vdpa: multiple address spaces support
   vdpa: introduce config operations for associating ASID to a virtqueue
     group
   vhost_iotlb: split out IOTLB initialization
   vhost: support ASID in IOTLB API
   vhost-vdpa: introduce asid based IOTLB
   vhost-vdpa: introduce uAPI to get the number of virtqueue groups
   vhost-vdpa: introduce uAPI to get the number of address spaces
   vhost-vdpa: uAPI to get virtqueue group id
   vhost-vdpa: introduce uAPI to set group ASID
   vhost-vdpa: support ASID based IOTLB API
   vdpa_sim: advertise VIRTIO_NET_F_MTU
   vdpa_sim: factor out buffer completion logic
   vdpa_sim: filter destination mac address
   vdpasim: control virtqueue support

  drivers/vdpa/ifcvf/ifcvf_main.c      |   8 +-
  drivers/vdpa/mlx5/net/mlx5_vnet.c    |  11 +-
  drivers/vdpa/vdpa.c                  |   5 +
  drivers/vdpa/vdpa_sim/vdpa_sim.c     | 100 ++++++++--
  drivers/vdpa/vdpa_sim/vdpa_sim.h     |   3 +
  drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 169 +++++++++++++----
  drivers/vhost/iotlb.c                |  23 ++-
  drivers/vhost/vdpa.c                 | 272 +++++++++++++++++++++------
  drivers/vhost/vhost.c                |  23 ++-
  drivers/vhost/vhost.h                |   4 +-
  drivers/virtio/virtio_vdpa.c         |   2 +-
  include/linux/vdpa.h                 |  46 ++++-
  include/linux/vhost_iotlb.h          |   2 +
  include/uapi/linux/vhost.h           |  25 ++-
  include/uapi/linux/vhost_types.h     |  11 +-
  15 files changed, 566 insertions(+), 138 deletions(-)





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