Re: [PATCH 3/5] qmp: Added the helper stamp check.

[Daniel P . Berrangé]

On Wed, Mar 22, 2023 at 03:26:59PM +0200, Andrew Melnichenko wrote:
> Hi all,
> I've researched an issue a bit. The solution with passing eBPF blob
> and loading in the Libvirt looks promising.
> Overall, the possible solution looks like this:
>  * Libvirt checks virtio-net properties and understands that eBPF
> steering may be required.
>  * Libvirt requests eBPF blob through QMP.
>  * Libvirt loads blob for virtio-net and passes fds from eBPF to QEMU.
> 
> I think that it's a good idea to pass only eBPF blob without
> additional metainformation. Most metainfo that we need could be
> retrieved from eBPF blob, and the only question is to pass fds
> sequence to QEMU.
> I propose to pass them as they appear in the blob itself, like
> "virtio-net-pci,ebpf_rss_fds=<prog>,<map1>,<map2>,<map3>...".

Using ',' for separating FDs is a bad idea, because ',' is already
used for separating QemuOpts arguments.

With -netdev we use ':' for spearating FDs with vhostfds= and fds=
arguments, so I'd suggest following that practice.

> Also, I think it's a good idea to make a "general" QMP request for
> eBPF blobs. Something like "request_ebpf <arg>"(g.e "request_ebpf
> virtio-net-rss").

That's reasonable as a future proofing idea I think.

With regards,
Daniel
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