Re: [PATCH v3 0/6] eBPF RSS through QMP support.

[Daniel P . Berrangé]

On Fri, Jun 30, 2023 at 01:06:22PM +0800, Jason Wang wrote:
> On Thu, Jun 15, 2023 at 6:29 AM Andrew Melnychenko <andrew@daynix.com> wrote:
> >
> > This series of patches provides the ability to retrieve eBPF program
> > through qmp, so management application may load bpf blob with proper 
> > capabilities.
> > Now, virtio-net devices can accept eBPF programs and maps through properties
> > as external file descriptors. Access to the eBPF map is direct through 
> > mmap()
> > call, so it should not require additional capabilities to bpf* calls.
> > eBPF file descriptors can be passed to QEMU from parent process or by unix
> > socket with sendfd() qmp command.
> >
> > Possible solution for libvirt may look like this: 
> > https://github.com/daynix/libvirt/tree/RSS_eBPF (WIP)
> >
> > Changes since v2:
> >  * moved/refactored QMP command
> >  * refactored virtio-net
> 
> I've queued this series, but a question left:
> 
> mmap() support for eBPF maps is not supported from day0, should we
> fallback to syscall for the OS that doesn't support that?

How recent is mmap() support ? Is it difficult to do a fallback ?

As since is a new feature, there's no inherant expectation of support
for arbitrary old platforms. So only worth investing in a fallback if
it is easy, or there's a very compelling reason to support certain
old platforms.


With regards,
Daniel
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