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From: David Gibson <david@gibson.dropbear.id.au>
To: Laurent Vivier <lvivier@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v5 4/4] vhost-user: add vhost-user
Date: Mon, 23 Sep 2024 13:59:51 +1000	[thread overview]
Message-ID: <ZvDnt3e1u_9KKnfl@zatzit.fritz.box> (raw)
In-Reply-To: <e19499b7-a9ab-4e47-a5dc-cd0f26b0afae@redhat.com>

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On Tue, Sep 17, 2024 at 12:03:13PM +0200, Laurent Vivier wrote:
> On 16/09/2024 09:00, David Gibson wrote:
> > > --- a/tap.c
> > > +++ b/tap.c
> > > @@ -58,6 +58,7 @@
> > >   #include "packet.h"
> > >   #include "tap.h"
> > >   #include "log.h"
> > > +#include "vhost_user.h"
> > >   /* IPv4 (plus ARP) and IPv6 message batches from tap/guest to IP handlers */
> > >   static PACKET_POOL_NOINIT(pool_tap4, TAP_MSGS, pkt_buf);
> > > @@ -78,16 +79,22 @@ void tap_send_single(const struct ctx *c, const void *data, size_t l2len)
> > >   	struct iovec iov[2];
> > >   	size_t iovcnt = 0;
> > > -	if (c->mode == MODE_PASST) {
> > > +	switch (c->mode) {
> > > +	case MODE_PASST:
> > >   		iov[iovcnt] = IOV_OF_LVALUE(vnet_len);
> > >   		iovcnt++;
> > > -	}
> > > -
> > > -	iov[iovcnt].iov_base = (void *)data;
> > > -	iov[iovcnt].iov_len = l2len;
> > > -	iovcnt++;
> > > +		/* fall through */
> > > +	case MODE_PASTA:
> > > +		iov[iovcnt].iov_base = (void *)data;
> > > +		iov[iovcnt].iov_len = l2len;
> > > +		iovcnt++;
> > > -	tap_send_frames(c, iov, iovcnt, 1);
> > > +		tap_send_frames(c, iov, iovcnt, 1);
> > > +		break;
> > > +	case MODE_VU:
> > > +		vu_send(c->vdev, data, l2len);
> > I'm a bit uneasy re-introducing a parallel send function for the slow
> > path, rather than using a common tap_send_frames() interface.  Any
> > chance you can unify those sensibly?  Bearing in mind that this_is_
> > the slow path, so if you have to copy a bunch of stuff, that's ok.
> 
> I tried but it's over complicated to take in input an iovec array and to use
> another iovec array (provided by the guest) to send data. It's easier to
> have a buffer and to copy it to the iovec array buffers of the guest.
> Moreover we don't need to have a tap_send_frames_vu() (see vu_handle_tx()),
> so we will introduce it to always send an iovec array with only one entry.

Oh, ok.  IIUC you're saying that both this path and the "main" path go
through vu_send(), in which case this is fine.

-- 
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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  reply	other threads:[~2024-09-23  4:11 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-09-13 16:20 [PATCH v5 0/4] Add vhost-user support to passt. (part 3) Laurent Vivier
2024-09-13 16:20 ` [PATCH v5 1/4] packet: replace struct desc by struct iovec Laurent Vivier
2024-09-13 16:20 ` [PATCH v5 2/4] vhost-user: introduce virtio API Laurent Vivier
2024-09-13 16:20 ` [PATCH v5 3/4] vhost-user: introduce vhost-user API Laurent Vivier
2024-09-13 16:20 ` [PATCH v5 4/4] vhost-user: add vhost-user Laurent Vivier
2024-09-16  7:00   ` David Gibson
2024-09-17 10:03     ` Laurent Vivier
2024-09-23  3:59       ` David Gibson [this message]
2024-09-19 13:51   ` Stefano Brivio
2024-09-23  4:11     ` David Gibson

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