vmxnet3 no longer functional on DPDK 21.11

[Bruce Richardson]

On Tue, Jan 09, 2024 at 07:46:47AM -0600, Lewis Donzis wrote:
> Hi, Bruce.
> 
> I'm even less familiar with it, but we do quite a lot of testing using VMs, so it's been quite handy.
> 
> Your patch seems very reasonable, however it also produces a warning:
> 
> ../drivers/net/vmxnet3/vmxnet3_ethdev.c:264:1: warning: unused function 'vmxnet3_enable_all_intrs' [-Wunused-function]
> 
> Adding an #ifndef around vmxnet3_enable_all_intrs() eliminates that warning.

Right, I should have compile-tested on FreeBSD myself, before sending the
suggestion. Patch has now been submitted. Please test and ack if the fix
works for your use-cases, thanks.

> 
> Please pardon the uninformed view, but we've been using FreeBSD + DPDK for nearly a decade, and I thought the whole point was to avoid using interrupts.  We have no need or desire for them in our applications, so we just hope the sprinkling of interrupt support code throughout the drivers doesn't cause any harm.  But I also realize we're probably in the minority on this.
> 
In general, yes we try and avoid interrupts on the data-path or fast-path
and use polling. However, for some use-cases where traffic levels are low,
interrupts may make sense to save power for fast-path. Even if not,
interrupts are useful for things like error conditions or for monitoring
link-status changes (LSC). Unfortunately, we don't have any interrupt
support on BSD, so fixes like this are necessary.

/Bruce