netdev - Re: [patch net-next v2 1/6] virtio: add debugfs infrastructure to allow to debug virtio features

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Date: Wed, 17 Apr 2024 12:37:30 +0800
From: Jason Wang <jasowang@...hat.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: netdev@...r.kernel.org, kuba@...nel.org, pabeni@...hat.com, 
	davem@...emloft.net, edumazet@...gle.com, parav@...dia.com, mst@...hat.com, 
	xuanzhuo@...ux.alibaba.com, shuah@...nel.org, petrm@...dia.com, 
	liuhangbin@...il.com, vladimir.oltean@....com, bpoirier@...dia.com, 
	idosch@...dia.com, virtualization@...ts.linux.dev
Subject: Re: [patch net-next v2 1/6] virtio: add debugfs infrastructure to
 allow to debug virtio features

On Tue, Apr 16, 2024 at 5:37 PM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Tue, Apr 16, 2024 at 05:52:41AM CEST, jasowang@...hat.com wrote:
> >On Tue, Apr 16, 2024 at 12:25 AM Jiri Pirko <jiri@...nulli.us> wrote:
> >>
> >> From: Jiri Pirko <jiri@...dia.com>
> >>
> >> Currently there is no way for user to set what features the driver
> >> should obey or not, it is hard wired in the code.
> >>
> >> In order to be able to debug the device behavior in case some feature is
> >> disabled, introduce a debugfs infrastructure with couple of files
> >> allowing user to see what features the device advertises and
> >> to set filter for features used by driver.
> >>
> >> Example:
> >> $cat /sys/bus/virtio/devices/virtio0/features
> >> 1110010111111111111101010000110010000000100000000000000000000000
> >> $ echo "5" >/sys/kernel/debug/virtio/virtio0/filter_feature_add
> >> $ cat /sys/kernel/debug/virtio/virtio0/filter_features
> >> 5
> >> $ echo "virtio0" > /sys/bus/virtio/drivers/virtio_net/unbind
> >> $ echo "virtio0" > /sys/bus/virtio/drivers/virtio_net/bind
> >> $ cat /sys/bus/virtio/devices/virtio0/features
> >> 1110000111111111111101010000110010000000100000000000000000000000
> >>
> >> Note that sysfs "features" know already exists, this patch does not
> >> touch it.
> >>
> >> Signed-off-by: Jiri Pirko <jiri@...dia.com>
> >> ---
> >
> >Note that this can be done already with vp_vdpa feature provisioning:
> >
> >commit c1ca352d371f724f7fb40f016abdb563aa85fe55
> >Author: Jason Wang <jasowang@...hat.com>
> >Date:   Tue Sep 27 15:48:10 2022 +0800
> >
> >    vp_vdpa: support feature provisioning
> >
> >For example:
> >
> >vdpa dev add name dev1 mgmtdev pci/0000:02:00.0 device_features 0x300020000
>
> Sure. My intension was to make the testing possible on any virtio
> device.

It did that actually, vp_vdpa bridge virtio-pci device into vDPA bus
with mediation layer (like feature filtering etc). So it can only run
on top of standard virtio-pci device.

> Narrowing the testing for vpda would be limitting.

Unless you want to use other transport like virtio-mmio.

Thanks

>
>
> >
> >Thanks
> >
>