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Subject[RFC PATCH 00/24] Control VQ support in vDPA
Date
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 accesing 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 refer
patch 24 for more implementation details.

Please review.

Note that patch 1 and a equivalent of patch 2 have been posted in the
list. Those two are requirement for this series to work, so I add them
here.

Thank

Jason Wang (24):
vhost-vdpa: fix backend feature ioctls
vhost-vdpa: fix vqs leak in vhost_vdpa_open()
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: add the missing comment for nvqs in struct vdpa_device
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: use separated iov for reading and writing
vdpa_sim: advertise VIRTIO_NET_F_MTU
vdpa_sim: advertise VIRTIO_NET_F_MAC
vdpa_sim: factor out buffer completion logic
vdpa_sim: filter destination mac address
vdpasim: control virtqueue support

drivers/vdpa/ifcvf/ifcvf_main.c | 9 +-
drivers/vdpa/mlx5/net/mlx5_vnet.c | 11 +-
drivers/vdpa/vdpa.c | 8 +-
drivers/vdpa/vdpa_sim/vdpa_sim.c | 293 ++++++++++++++++++++++++------
drivers/vhost/iotlb.c | 23 ++-
drivers/vhost/vdpa.c | 259 ++++++++++++++++++++------
drivers/vhost/vhost.c | 23 ++-
drivers/vhost/vhost.h | 4 +-
drivers/virtio/virtio_vdpa.c | 2 +-
include/linux/vdpa.h | 42 ++++-
include/linux/vhost_iotlb.h | 2 +
include/uapi/linux/vhost.h | 19 +-
include/uapi/linux/vhost_types.h | 10 +-
13 files changed, 556 insertions(+), 149 deletions(-)

--
2.20.1

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