On Tue, 16 Apr 2019 10:59:37 +0200, Jiri Pirko wrote:
> >> 4) netdevsim instances are created by "ip link add" which is great for
> >> soft devices with no hw backend. The rtnl core allocates netdev and
> >> calls into driver holding rtnl mutex. For hw-backed devices, this
> >> flow is wrong as it breaks order in which things are done.
> >>
> >> This patchset adjust netdevsim to fix all above.
> >>
> >> In order to support proper devlink and devlink port instances and to be
> >> able to emulate real devices, there is need to implement bus probe and
> >> instantiate everything from there. User can specify device id and port
> >> count to be instantianted. For example:
> >>
> >> echo "10 4" > /sys/bus/netdevsim/new_device
> >
> >I really don't like the design where ID has to be allocated by user
> >space. It's a step back.
> >
> >I also dislike declaring ports from the start. In real drivers ports
> >are never "atomically" registered, they are crated and destroyed one
>
> Care to define "atomically" here? It is done in a very similar way
> to how it is done in mlxsw for example. Same flows.
>
>
> >by one, and a lot of races/UAFs/bugs lie in those small periods of
> >time where one netdev got unregistered, but other are still around...
>
> Same here. Not sure where do you see the differences.
The difference is that today I can do this:
create a netdevsim1 with shared dev 1
create some state associated with shared dev 1
create a netdevsim2 with shared dev 1
check if all the shared dev 1 state created for netdevsim1 is visible
via netdevsim2
destroy netdevsim1
check the shared dev 1 state again
If I say "give me 2 ports" from the start, that makes the testing
(which is the whole point of this code) harder.
> Also, I plan to implement port splitting in follow-up patchset. All
> flows are there as well.
Sure, let's just be clear that we won't be merging an ABI that has just
a netdevsim implementation, right? I have some reservations about the
"port splitting" or device slicing, which should be discussed over real
code, not netdevsim.
