Is QEMU's vmxnet3 still being used?

Is QEMU's vmxnet3 still being used?

[Thomas Huth]

  Hi all,

I recently noticed that we have quite a bunch of tickets against the vmxnet3 
device in our bug trackers, which indicate that this device could be used to 
crash QEMU in various ways:

  https://gitlab.com/qemu-project/qemu/-/issues?state=opened&search=vmxnet3

  https://bugs.launchpad.net/qemu?field.searchtext=vmxnet3

Having hardly any knowledge about this device and its usage at all, I wonder 
how much it is still used out there in the wild? If there are still many 
users of this device, is there anybody interested here in helping to get 
these crashes fixed in the near future? Otherwise, should we maybe rather 
mark this device as deprecated and remove it in a couple of releases? What 
do you think?

  Thomas

Re: Is QEMU's vmxnet3 still being used?

[Jason Wang]

On Wed, Aug 18, 2021 at 9:42 PM Thomas Huth <thuth@redhat.com> wrote:
>
>
>   Hi all,
>
> I recently noticed that we have quite a bunch of tickets against the vmxnet3
> device in our bug trackers, which indicate that this device could be used to
> crash QEMU in various ways:
>
>   https://gitlab.com/qemu-project/qemu/-/issues?state=opened&search=vmxnet3
>
>   https://bugs.launchpad.net/qemu?field.searchtext=vmxnet3
>
> Having hardly any knowledge about this device and its usage at all, I wonder
> how much it is still used out there in the wild?

I guess it might have been used for virt-v2v in the past.

But I'm not sure what's the status now.

Thanks

> If there are still many
> users of this device, is there anybody interested here in helping to get
> these crashes fixed in the near future? Otherwise, should we maybe rather
> mark this device as deprecated and remove it in a couple of releases? What
> do you think?
>
>   Thomas
>

Re: Is QEMU's vmxnet3 still being used?

[Yan Vugenfirer]

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Hi All,

I know it is used to develop DPDK support on Windows right now.
Previously it was used for different nested virtualization scenarios as
well.

Best regards,
Yan.

On Thu, Aug 19, 2021 at 11:22 AM Jason Wang <jasowang@redhat.com> wrote:

> On Wed, Aug 18, 2021 at 9:42 PM Thomas Huth <thuth@redhat.com> wrote:
> >
> >
> >   Hi all,
> >
> > I recently noticed that we have quite a bunch of tickets against the
> vmxnet3
> > device in our bug trackers, which indicate that this device could be
> used to
> > crash QEMU in various ways:
> >
> >
> https://gitlab.com/qemu-project/qemu/-/issues?state=opened&search=vmxnet3
> >
> >   https://bugs.launchpad.net/qemu?field.searchtext=vmxnet3
> >
> > Having hardly any knowledge about this device and its usage at all, I
> wonder
> > how much it is still used out there in the wild?
>
> I guess it might have been used for virt-v2v in the past.
>
> But I'm not sure what's the status now.
>
> Thanks
>
> > If there are still many
> > users of this device, is there anybody interested here in helping to get
> > these crashes fixed in the near future? Otherwise, should we maybe rather
> > mark this device as deprecated and remove it in a couple of releases?
> What
> > do you think?
> >
> >   Thomas
> >
>
>
>

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Re: Is QEMU's vmxnet3 still being used?

[Daniel P. Berrangé]

On Wed, Aug 18, 2021 at 03:42:23PM +0200, Thomas Huth wrote:
> 
>  Hi all,
> 
> I recently noticed that we have quite a bunch of tickets against the vmxnet3
> device in our bug trackers, which indicate that this device could be used to
> crash QEMU in various ways:
> 
>  https://gitlab.com/qemu-project/qemu/-/issues?state=opened&search=vmxnet3
> 
>  https://bugs.launchpad.net/qemu?field.searchtext=vmxnet3

IIUC, all except 3 of those bugs, are issues from the device fuzzer.

It is nice that we find those, but if we don't consider this a device
targetted at virtualization use cases, I don't think they're a reason
to remove the device.

> Having hardly any knowledge about this device and its usage at all, I wonder
> how much it is still used out there in the wild? If there are still many
> users of this device, is there anybody interested here in helping to get
> these crashes fixed in the near future? Otherwise, should we maybe rather
> mark this device as deprecated and remove it in a couple of releases? What
> do you think?

We've got countless NIC models in QEMU most of which have minimal users,
are possibly buggy, not actively maintained, but exist to support
non-virtualization use cases. We've especially not had "how many users
are there" as a criteria for acceptance or removal of a device.

Regards,
Daniel
-- 
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Re: Is QEMU's vmxnet3 still being used?

[Peter Maydell]

On Thu, 19 Aug 2021 at 09:54, Daniel P. Berrangé <berrange@redhat.com> wrote:
> We've especially not had "how many users
> are there" as a criteria for acceptance or removal of a device.

...not least because we have no accurate way to determine
the answer to that question!

-- PMM

Re: Is QEMU's vmxnet3 still being used?

[Markus Armbruster]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Thu, 19 Aug 2021 at 09:54, Daniel P. Berrangé <berrange@redhat.com> wrote:
>> We've especially not had "how many users
>> are there" as a criteria for acceptance or removal of a device.
>
> ...not least because we have no accurate way to determine
> the answer to that question!

I'd like to posit an approximate answer: "enough" if somebody is willing
to provide basic care for the code, else "not enough".

"Basic care" includes taking care of known bugs.  CLOSED/WONTFIX because
$reasons is an option.  Not even looking is not.

Re: Is QEMU's vmxnet3 still being used?

[Markus Armbruster]

Daniel P. Berrangé <berrange@redhat.com> writes:

> On Wed, Aug 18, 2021 at 03:42:23PM +0200, Thomas Huth wrote:
>> 
>>  Hi all,
>> 
>> I recently noticed that we have quite a bunch of tickets against the vmxnet3
>> device in our bug trackers, which indicate that this device could be used to
>> crash QEMU in various ways:
>> 
>>  https://gitlab.com/qemu-project/qemu/-/issues?state=opened&search=vmxnet3
>> 
>>  https://bugs.launchpad.net/qemu?field.searchtext=vmxnet3
>
> IIUC, all except 3 of those bugs, are issues from the device fuzzer.
>
> It is nice that we find those, but if we don't consider this a device
> targetted at virtualization use cases, I don't think they're a reason
> to remove the device.
>
>> Having hardly any knowledge about this device and its usage at all, I wonder
>> how much it is still used out there in the wild? If there are still many
>> users of this device, is there anybody interested here in helping to get
>> these crashes fixed in the near future? Otherwise, should we maybe rather
>> mark this device as deprecated and remove it in a couple of releases? What
>> do you think?
>
> We've got countless NIC models in QEMU most of which have minimal users,
> are possibly buggy, not actively maintained, but exist to support
> non-virtualization use cases. We've especially not had "how many users
> are there" as a criteria for acceptance or removal of a device.

I accept "good enough for intended use", and that certain kinds of bugs
are much less serious in emulation use than in virtualization use.

Still, there's a difference between "possibly buggy" and "perennially
unmaintained / can't even be bothered to fix known bugs".  Why should we
carry code that isn't of sufficient interest to anyone to motivate basic
care?

Moreover, having drastically different code quality requirements in the
tree is problematic.  Compounded by them being less than obvious.  If
people knew nobody cared for bugs in hw/mumble/mutter.c, they could save
themselves the trouble of fuzzing or otherwise examining it.  They might
even be dissuaded from copying (quite possibly bad) code from it.

I do believe the way we operate promotes misallocation of (scarce)
resources.