Re: [PATCH v11 5/5] docs: Add generic vhost-vdpa device documentation

[Michael S. Tsirkin]

On Tue, Dec 20, 2022 at 08:02:51AM +0800, Longpeng (Mike, Cloud Infrastructure 
Service Product Dept.) wrote:
> 
> 
> 在 2022/12/20 5:37, Michael S. Tsirkin 写道:
> > On Fri, Dec 16, 2022 at 11:33:49AM +0800, Jason Wang wrote:
> > > On Thu, Dec 15, 2022 at 9:50 PM Longpeng(Mike) <longpeng2@huawei.com> 
> > > wrote:
> > > > 
> > > > From: Longpeng <longpeng2@huawei.com>
> > > > 
> > > > Signed-off-by: Longpeng <longpeng2@huawei.com>
> > > > ---
> > > >   .../devices/vhost-vdpa-generic-device.rst     | 68 +++++++++++++++++++
> > > >   1 file changed, 68 insertions(+)
> > > >   create mode 100644 docs/system/devices/vhost-vdpa-generic-device.rst
> > > > 
> > > > diff --git a/docs/system/devices/vhost-vdpa-generic-device.rst 
> > > > b/docs/system/devices/vhost-vdpa-generic-device.rst
> > > > new file mode 100644
> > > > index 0000000000..24c825ef1a
> > > > --- /dev/null
> > > > +++ b/docs/system/devices/vhost-vdpa-generic-device.rst
> > > > @@ -0,0 +1,68 @@
> > > > +
> > > > +=========================
> > > > +vhost-vDPA generic device
> > > > +=========================
> > > > +
> > > > +This document explains the usage of the vhost-vDPA generic device.
> > > > +
> > > > +
> > > > +Description
> > > > +-----------
> > > > +
> > > > +vDPA(virtio data path acceleration) device is a device that uses a 
> > > > datapath
> > > > +which complies with the virtio specifications with vendor specific 
> > > > control
> > > > +path.
> > > > +
> > > > +QEMU provides two types of vhost-vDPA devices to enable the vDPA 
> > > > device, one
> > > > +is type sensitive which means QEMU needs to know the actual device type
> > > > +(e.g. net, blk, scsi) and another is called "vhost-vDPA generic 
> > > > device" which
> > > > +is type insensitive.
> > > > +
> > > > +The vhost-vDPA generic device builds on the vhost-vdpa subsystem and 
> > > > virtio
> > > > +subsystem. It is quite small, but it can support any type of virtio 
> > > > device.
> > > > +
> > > > +
> > > > +Requirements
> > > > +------------
> > > > +Linux 5.18+
> > > > +iproute2/vdpa 5.12.0+
> > > > +
> > > > +
> > > > +Examples
> > > > +--------
> > > > +
> > > > +1. Prepare the vhost-vDPA backends, here is an example using 
> > > > vdpa_sim_blk
> > > > +   device:
> > > > +
> > > > +::
> > > > +  host# modprobe vhost_vdpa
> > > > +  host# modprobe vdpa_sim_blk
> > > 
> > > Nit: it's probably better to add driver binding steps here.
> > > 
> > > > +  host# vdpa dev add mgmtdev vdpasim_blk name blk0
> > > > +  (...you can see the vhost-vDPA device under /dev directory now...)
> > > 
> > > And then the vhost char dev name could be fetch via
> > > 
> > > ls /sys/bus/vdpa/device/blk0/vhost-vdpa*
> > > 
> > > With the above changes.
> > > 
> > > Acked-by: Jason Wang <jasowang@redhat.com>
> > > 
> > > Thanks
> > 
> > 
> > Sounds minor enough, I'll queue, pls fix with a patch on top.
> > 
> OK, thanks. I'll send when I'm free.

Is this going to be in the next couple of weeks? then ok.
We do want this addressed by let's say rc3.

> > > > +  host# ls -l /dev/vhost-vdpa-*
> > > > +  crw------- 1 root root 236, 0 Nov  2 00:49 /dev/vhost-vdpa-0
> > > > +
> > > > +Note:
> > > > +It needs some vendor-specific steps to provision the vDPA device if 
> > > > you're
> > > > +using real HW devices, such as loading the vendor-specific vDPA driver 
> > > > and
> > > > +binding the device to the driver.
> > > > +
> > > > +
> > > > +2. Start the virtual machine:
> > > > +
> > > > +Start QEMU with virtio-mmio bus:
> > > > +
> > > > +::
> > > > +  host# qemu-system                                                  \
> > > > +      -M microvm -m 512 -smp 2 -kernel ... -initrd ...               \
> > > > +      -device vhost-vdpa-device,vhostdev=/dev/vhost-vdpa-0           \
> > > > +      ...
> > > > +
> > > > +
> > > > +Start QEMU with virtio-pci bus:
> > > > +
> > > > +::
> > > > +  host# qemu-system                                                  \
> > > > +      -M pc -m 512 -smp 2                                            \
> > > > +      -device vhost-vdpa-device-pci,vhostdev=/dev/vhost-vdpa-0       \
> > > > +      ...
> > > > --
> > > > 2.23.0
> > > > 
> > 
> > .