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Date: Mon, 30 Nov 2020 15:07:04 +0800
From: Yongji Xie <xieyongji@...edance.com>
To: Jason Wang <jasowang@...hat.com>
Cc: Parav Pandit <parav@...dia.com>,
virtualization@...ts.linux-foundation.org,
"Michael S. Tsirkin" <mst@...hat.com>, elic@...dia.com,
netdev@...r.kernel.org
Subject: Re: [External] Re: [PATCH 0/7] Introduce vdpa management tool
On Mon, Nov 30, 2020 at 11:36 AM Jason Wang <jasowang@...hat.com> wrote:
>
>
> On 2020/11/27 下午1:52, Yongji Xie wrote:
> > On Fri, Nov 27, 2020 at 11:53 AM Jason Wang <jasowang@...hat.com
> > <mailto:jasowang@...hat.com>> wrote:
> >
> >
> > On 2020/11/12 下午2:39, Parav Pandit wrote:
> > > This patchset covers user requirements for managing existing
> > vdpa devices,
> > > using a tool and its internal design notes for kernel drivers.
> > >
> > > Background and user requirements:
> > > ----------------------------------
> > > (1) Currently VDPA device is created by driver when driver is
> > loaded.
> > > However, user should have a choice when to create or not create
> > a vdpa device
> > > for the underlying parent device.
> > >
> > > For example, mlx5 PCI VF and subfunction device supports
> > multiple classes of
> > > device such netdev, vdpa, rdma. Howevever it is not required to
> > always created
> > > vdpa device for such device.
> > >
> > > (2) In another use case, a device may support creating one or
> > multiple vdpa
> > > device of same or different class such as net and block.
> > > Creating vdpa devices at driver load time further limits this
> > use case.
> > >
> > > (3) A user should be able to monitor and query vdpa queue level
> > or device level
> > > statistics for a given vdpa device.
> > >
> > > (4) A user should be able to query what class of vdpa devices
> > are supported
> > > by its parent device.
> > >
> > > (5) A user should be able to view supported features and
> > negotiated features
> > > of the vdpa device.
> > >
> > > (6) A user should be able to create a vdpa device in vendor
> > agnostic manner
> > > using single tool.
> > >
> > > Hence, it is required to have a tool through which user can
> > create one or more
> > > vdpa devices from a parent device which addresses above user
> > requirements.
> > >
> > > Example devices:
> > > ----------------
> > > +-----------+ +-----------+ +---------+ +--------+ +-----------+
> > > |vdpa dev 0 | |vdpa dev 1 | |rdma dev | |netdev | |vdpa dev 3 |
> > > |type=net | |type=block | |mlx5_0 | |ens3f0 | |type=net |
> > > +----+------+ +-----+-----+ +----+----+ +-----+--+ +----+------+
> > > | | | | |
> > > | | | | |
> > > +----+-----+ | +----+----+ | +----+----+
> > > | mlx5 +--------+ |mlx5 +-------+ |mlx5 |
> > > |pci vf 2 | |pci vf 4 | |pci sf 8 |
> > > |03:00:2 | |03:00.4 | |mlx5_sf.8|
> > > +----+-----+ +----+----+ +----+----+
> > > | | |
> > > | +----+-----+ |
> > > +----------------------+mlx5 +----------------+
> > > |pci pf 0 |
> > > |03:00.0 |
> > > +----------+
> > >
> > > vdpa tool:
> > > ----------
> > > vdpa tool is a tool to create, delete vdpa devices from a parent
> > device. It is a
> > > tool that enables user to query statistics, features and may be
> > more attributes
> > > in future.
> > >
> > > vdpa tool command draft:
> > > ------------------------
> > > (a) List parent devices which supports creating vdpa devices.
> > > It also shows which class types supported by this parent device.
> > > In below command example two parent devices support vdpa device
> > creation.
> > > First is PCI VF whose bdf is 03.00:2.
> > > Second is PCI VF whose name is 03:00.4.
> > > Third is PCI SF whose name is mlx5_core.sf.8
> > >
> > > $ vdpa parentdev list
> > > vdpasim
> > > supported_classes
> > > net
> > > pci/0000:03.00:3
> > > supported_classes
> > > net block
> > > pci/0000:03.00:4
> > > supported_classes
> > > net block
> > > auxiliary/mlx5_core.sf.8
> > > supported_classes
> > > net
> > >
> > > (b) Now add a vdpa device of networking class and show the device.
> > > $ vdpa dev add parentdev pci/0000:03.00:2 type net name foo0 $
> > vdpa dev show foo0
> > > foo0: parentdev pci/0000:03.00:2 type network parentdev vdpasim
> > vendor_id 0 max_vqs 2 max_vq_size 256
> > >
> > > (c) Show features of a vdpa device
> > > $ vdpa dev features show foo0
> > > supported
> > > iommu platform
> > > version 1
> > >
> > > (d) Dump vdpa device statistics
> > > $ vdpa dev stats show foo0
> > > kickdoorbells 10
> > > wqes 100
> > >
> > > (e) Now delete a vdpa device previously created.
> > > $ vdpa dev del foo0
> > >
> > > vdpa tool support in this patchset:
> > > -----------------------------------
> > > vdpa tool is created to create, delete and query vdpa devices.
> > > examples:
> > > Show vdpa parent device that supports creating, deleting vdpa
> > devices.
> > >
> > > $ vdpa parentdev show
> > > vdpasim:
> > > supported_classes
> > > net
> > >
> > > $ vdpa parentdev show -jp
> > > {
> > > "show": {
> > > "vdpasim": {
> > > "supported_classes": {
> > > "net"
> > > }
> > > }
> > > }
> > >
> > > Create a vdpa device of type networking named as "foo2" from the
> > parent device vdpasim:
> > >
> > > $ vdpa dev add parentdev vdpasim type net name foo2
> > >
> > > Show the newly created vdpa device by its name:
> > > $ vdpa dev show foo2
> > > foo2: type network parentdev vdpasim vendor_id 0 max_vqs 2
> > max_vq_size 256
> > >
> > > $ vdpa dev show foo2 -jp
> > > {
> > > "dev": {
> > > "foo2": {
> > > "type": "network",
> > > "parentdev": "vdpasim",
> > > "vendor_id": 0,
> > > "max_vqs": 2,
> > > "max_vq_size": 256
> > > }
> > > }
> > > }
> > >
> > > Delete the vdpa device after its use:
> > > $ vdpa dev del foo2
> > >
> > > vdpa tool support by kernel:
> > > ----------------------------
> > > vdpa tool user interface will be supported by existing vdpa
> > kernel framework,
> > > i.e. drivers/vdpa/vdpa.c It services user command through a
> > netlink interface.
> > >
> > > Each parent device registers supported callback operations with
> > vdpa subsystem
> > > through which vdpa device(s) can be managed.
> > >
> > > FAQs:
> > > -----
> > > 1. Where does userspace vdpa tool reside which users can use?
> > > Ans: vdpa tool can possibly reside in iproute2 [1] as it enables
> > user to
> > > create vdpa net devices.
> > >
> > > 2. Why not create and delete vdpa device using sysfs/configfs?
> > > Ans:
> > > (a) A device creation may involve passing one or more attributes.
> > > Passing multiple attributes and returning error code and more
> > verbose
> > > information for invalid attributes cannot be handled by
> > sysfs/configfs.
> > >
> > > (b) netlink framework is rich that enables user space and kernel
> > driver to
> > > provide nested attributes.
> > >
> > > (c) Exposing device specific file under sysfs without net namespace
> > > awareness exposes details to multiple containers. Instead exposing
> > > attributes via a netlink socket secures the communication
> > channel with kernel.
> > >
> > > (d) netlink socket interface enables to run syscaller kernel tests.
> > >
> > > 3. Why not use ioctl() interface?
> > > Ans: ioctl() interface replicates the necessary plumbing which
> > already
> > > exists through netlink socket.
> > >
> > > 4. What happens when one or more user created vdpa devices exist
> > for a
> > > parent PCI VF or SF and such parent device is removed?
> > > Ans: All user created vdpa devices are removed that belong to a
> > parent.
> > >
> > > [1]
> > git://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git
> > <http://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git>
> > >
> > > Next steps:
> > > -----------
> > > (a) Post this patchset and iproute2/vdpa inclusion, remaining
> > two drivers
> > > will be coverted to support vdpa tool instead of creating
> > unmanaged default
> > > device on driver load.
> > > (b) More net specific parameters such as mac, mtu will be added.
> > > (c) Features bits get and set interface will be added.
> >
> >
> > Adding Yong Ji for sharing some thoughts from the view of
> > userspace vDPA
> > device.
> >
> >
> > Thanks for adding me, Jason!
> >
> > Now I'm working on a v2 patchset for VDUSE (vDPA Device in Userspace)
> > [1]. This tool is very useful for the vduse device. So I'm considering
> > integrating this into my v2 patchset. But there is one problem：
> >
> > In this tool, vdpa device config action and enable action are combined
> > into one netlink msg: VDPA_CMD_DEV_NEW. But in vduse case, it needs to
> > be splitted because a chardev should be created and opened by a
> > userspace process before we enable the vdpa device (call
> > vdpa_register_device()).
> >
> > So I'd like to know whether it's possible (or have some plans) to add
> > two new netlink msgs something like: VDPA_CMD_DEV_ENABLE and
> > VDPA_CMD_DEV_DISABLE to make the config path more flexible.
> >
>
> Actually, we've discussed such intermediate step in some early
> discussion. It looks to me VDUSE could be one of the users of this.
>
> Or I wonder whether we can switch to use anonymous inode(fd) for VDUSE
> then fetching it via an VDUSE_GET_DEVICE_FD ioctl?
>
Yes, we can. Actually the current implementation in VDUSE is like
this. But seems like this is still a intermediate step. The fd should
be binded to a name or something else which need to be configured
before.
Thanks,
Yongji
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