Re: [PATCH v3 04/10] udp_vu: Move virtqueue management from udp_vu_sock_recv() to its caller

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, May 11, 2026 at 05:30:33AM -0400, Jon Maloy wrote:
> 
> 
> On 2026-04-16 11:57, Laurent Vivier wrote:
> > udp_vu_sock_recv() currently mixes two concerns: receiving data from the
> > socket and managing virtqueue buffers (collecting, rewinding, releasing).
> > This makes the function harder to reason about and couples socket I/O
> > with virtqueue state.
> > 
> > Move all virtqueue operations, vu_collect(), vu_init_elem(),
> > vu_queue_rewind(), vu_set_vnethdr(), and the queue-readiness check, into
> > udp_vu_sock_to_tap(), which is the only caller.  This turns
> > udp_vu_sock_recv() into a pure socket receive function that simply reads
> > into the provided iov array and adjusts its length.
> > 
> > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> 
> Reviewed-by: Jon Maloy <jmaloy@redhat.com>
> 
> see below.
> 
> > ---
> >   udp_vu.c | 98 +++++++++++++++++++++++++++++---------------------------
> >   1 file changed, 50 insertions(+), 48 deletions(-)
> > 
> > diff --git a/udp_vu.c b/udp_vu.c
> > index f8629af58ab5..bd9fd5abb971 100644
> > --- a/udp_vu.c
> [...]
> > +
> > +	if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
> > +		struct msghdr msg = { 0 };
> > +
> > +		debug("Got UDP packet, but RX virtqueue not usable yet");
> > +
> > +		for (i = 0; i < n; i++) {
> > +			if (recvmsg(s, &msg, MSG_DONTWAIT) < 0)
> > +				debug_perror("Failed to discard datagram");
> > +		}
> > +
> > +		return;
> > +	}
> > +
> >   	for (i = 0; i < n; i++) {
> > +		unsigned elem_cnt, elem_used;
> 
> unsigned int is standard in our code, I think.

I think Laurent has usually used 'unsigned int', but I've usually used
'unsigned'.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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