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

[Eugenio Perez Martin <eperezma@redhat.com>]

On Wed, Mar 30, 2022 at 8:05 PM Gautam Dawar <gautam.dawar@xilinx.com> wrote:
>
> 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 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 RFC v2:
>
> - Fixed memory leak for asid 0 in vhost_vdpa_remove_as()
> - Removed unnecessary NULL check for iotlb in vhost_vdpa_unmap() and
>   changed its return type to void.
> - Removed insignificant used_as member field from struct vhost_vdpa.
> - Corrected the iommu parameter in call to vringh_set_iotlb() from
>   vdpasim_set_group_asid()
> - Fixed build errors with vdpa_sim_net
> - Updated alibaba, vdpa_user and virtio_pci vdpa parent drivers to
>   call updated vDPA APIs and ensured successful build
> - Tested control (MAC address configuration) and data-path using
>   single virtqueue pair on Xilinx (now AMD) SN1022 SmartNIC device
>   and vdpa_sim_net software device using QEMU release at [1]
> - Removed two extra blank lines after set_group_asid() in
>   include/linux/vdpa.h
>
> 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
> - 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 [1]
>
> 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()
>
> [1] Development QEMU release with support for SVQ, VQ groups and ASID:
>   github.com/eugpermar/qemu/releases/tag/vdpa_sw_live_migration.d%2F
>   asid_groups-v1.d%2F00
>
> 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/alibaba/eni_vdpa.c      |   2 +-
>  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/vdpa/vdpa_user/vduse_dev.c   |   3 +-
>  drivers/vdpa/virtio_pci/vp_vdpa.c    |   2 +-
>  drivers/vhost/iotlb.c                |  23 ++-
>  drivers/vhost/vdpa.c                 | 267 +++++++++++++++++++++------
>  drivers/vhost/vhost.c                |  23 ++-
>  drivers/vhost/vhost.h                |   4 +-
>  drivers/virtio/virtio_vdpa.c         |   2 +-
>  include/linux/vdpa.h                 |  44 ++++-
>  include/linux/vhost_iotlb.h          |   2 +
>  include/uapi/linux/vhost.h           |  26 ++-
>  include/uapi/linux/vhost_types.h     |  11 +-
>  18 files changed, 563 insertions(+), 142 deletions(-)
>

Hoping it's not too late for this, but I tested this series with my
latest qemu CVQ SVQ RFC (v8). So, in that regard,

Reviewed-by: Eugenio Pérez <eperezma@redhat.com>