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From: David Marchand <david.marchand@redhat.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: dev <dev@dpdk.org>, Olivier Matz <olivier.matz@6wind.com>,
	 Flavio Leitner <fbl@sysclose.org>,
	Ilya Maximets <i.maximets@ovn.org>,
	Chenbo Xia <chenbo.xia@intel.com>,
	"Stokes, Ian" <ian.stokes@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2 4/4] vhost: fix offload flags in Rx path
Date: Thu, 29 Apr 2021 22:21:06 +0200
Message-ID: <CAJFAV8zLft93Btnt2gigXwOJ0N3kX=CuLKvSCtaX9aDWqrjAWA@mail.gmail.com> (raw)
In-Reply-To: <54d907c8-a49a-0ccb-2886-4a27474860c1@redhat.com>

On Thu, Apr 29, 2021 at 3:31 PM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
> On 4/29/21 3:30 PM, Maxime Coquelin wrote:
> >> The vhost library current configures Tx offloading (PKT_TX_*) on any
> >> packet received from a guest virtio device which asks for some offloading.
> >>
> >> This is problematic, as Tx offloading is something that the application
> >> must ask for: the application needs to configure devices
> >> to support every used offloads (ip, tcp checksumming, tso..), and the
> >> various l2/l3/l4 lengths must be set following any processing that
> >> happened in the application itself.
> >>
> >> On the other hand, the received packets are not marked wrt current
> >> packet l3/l4 checksumming info.
> >>
> >> Copy virtio rx processing to fix those offload flags but accepting
> >> VIRTIO_NET_HDR_GSO_ECN and VIRTIO_NET_HDR_GSO_UDP too.
> >>
> >> The vhost example has been updated accordingly: TSO is applied to any
> >> packet marked LRO.
> >>
> >> Fixes: 859b480d5afd ("vhost: add guest offload setting")
>
> As I understand it, this change kind of break the ABI, but it is
> actually fixing a misuse of the mbuf API, so I think we should
> take this patch.

Indeed, this breaks the v21 ABI.

But the only usecase I can think of is an application using TSO /
checksum offloads *only* for traffic coming from vhost.
I say *only* for traffic coming from vhost, because to have this
application do TSO / checksum offloaing for traffic coming from a
physical port, it would comply with the mbuf API and set the PKT_TX_*
flags.

Apart from the example/vhost, I am not sure there is such an
application that only does v2v or v2p but _not_ p2v TSO / checksum
offloading.
(Note: I am unable to use this example... it seems unhappy with the
mlx5 port I use => FPE because this driver does not support vmdq o_O)


I see three options:
- fix the vhost library and break the ABI that only works in an
example (this current patch),
- maintain the v21 ABI
  * using symbol versioning, this adds no branch, recompiled
application use the new ABI, this can't be backported to 20.11,
  * keeping the current behavior by default, but introducing a new
flag that an application would pass to rte_vhost_driver_register().
This new flag triggers this current patch behavior but it would add an
additional branch per packets bulk in vhost dequeue path. This *could*
be backported to 20.11.


-- 
David Marchand


  reply	other threads:[~2021-04-29 20:21 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01  9:52 [dpdk-dev] [PATCH 0/5] Offload flags fixes David Marchand
2021-04-01  9:52 ` [dpdk-dev] [PATCH 1/5] mbuf: mark old offload flag as deprecated David Marchand
2021-04-07 20:14   ` Flavio Leitner
2021-04-08  7:23   ` Olivier Matz
2021-04-08  8:41     ` David Marchand
2021-04-01  9:52 ` [dpdk-dev] [PATCH 2/5] net/tap: do not touch Tx offload flags David Marchand
2021-04-07 20:15   ` Flavio Leitner
2021-04-08  7:41     ` Olivier Matz
2021-04-08 11:21       ` Flavio Leitner
2021-04-08 12:05         ` Olivier Matz
2021-04-08 12:58           ` Flavio Leitner
2021-04-09 13:30             ` Olivier Matz
2021-04-09 16:55               ` Flavio Leitner
2021-04-28 12:17               ` David Marchand
2021-04-08 12:16         ` Ananyev, Konstantin
2021-04-08  7:53   ` Olivier Matz
2021-04-28 12:12     ` David Marchand
2021-04-01  9:52 ` [dpdk-dev] [PATCH 3/5] net/virtio: " David Marchand
2021-04-13 14:17   ` Maxime Coquelin
2021-04-01  9:52 ` [dpdk-dev] [PATCH 4/5] net/virtio: refactor Tx offload helper David Marchand
2021-04-08 13:05   ` Flavio Leitner
2021-04-09  2:31   ` Ruifeng Wang
2021-04-01  9:52 ` [dpdk-dev] [PATCH 5/5] vhost: fix offload flags in Rx path David Marchand
2021-04-08  8:28   ` Olivier Matz
2021-04-08 18:38   ` Flavio Leitner
2021-04-13 15:27     ` Maxime Coquelin
2021-04-27 17:09       ` David Marchand
2021-04-27 17:19         ` David Marchand
2021-04-29  8:04 ` [dpdk-dev] [PATCH v2 0/4] Offload flags fixes David Marchand
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 1/4] mbuf: mark old offload flag as deprecated David Marchand
2021-04-29 12:14     ` Lance Richardson
2021-04-29 16:45     ` Ajit Khaparde
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 2/4] net/virtio: do not touch Tx offload flags David Marchand
2021-04-29 13:51     ` Flavio Leitner
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 3/4] net/virtio: refactor Tx offload helper David Marchand
2021-04-29 12:59     ` Maxime Coquelin
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 4/4] vhost: fix offload flags in Rx path David Marchand
2021-04-29 13:30     ` Maxime Coquelin
2021-04-29 13:31       ` Maxime Coquelin
2021-04-29 20:21         ` David Marchand [this message]
2021-04-30  8:38           ` Maxime Coquelin
2021-04-29 20:09       ` David Marchand
2021-04-29 18:39     ` Flavio Leitner
2021-04-29 19:18       ` David Marchand
2021-05-03 13:26 ` [dpdk-dev] [PATCH v3 0/4] Offload flags fixes David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 1/4] mbuf: mark old offload flag as deprecated David Marchand
2021-05-03 14:02     ` Maxime Coquelin
2021-05-03 14:12     ` David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 2/4] net/virtio: do not touch Tx offload flags David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 3/4] net/virtio: refactor Tx offload helper David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 4/4] vhost: fix offload flags in Rx path David Marchand
2021-05-03 15:24   ` [dpdk-dev] [PATCH v3 0/4] Offload flags fixes Maxime Coquelin
2021-05-03 16:21     ` David Marchand
2021-05-03 16:43 ` [dpdk-dev] [PATCH v4 0/3] " David Marchand
2021-05-03 16:43   ` [dpdk-dev] [PATCH v4 1/3] net/virtio: do not touch Tx offload flags David Marchand
2021-05-03 16:43   ` [dpdk-dev] [PATCH v4 2/3] net/virtio: refactor Tx offload helper David Marchand
2021-05-03 16:43   ` [dpdk-dev] [PATCH v4 3/3] vhost: fix offload flags in Rx path David Marchand
2021-05-04 11:07     ` Flavio Leitner
2021-05-08  6:24     ` Wang, Yinan
2021-05-12  3:29       ` Wang, Yinan
2021-05-12 15:20         ` David Marchand
2021-05-13  6:34           ` Wang, Yinan
2021-05-04  8:29   ` [dpdk-dev] [PATCH v4 0/3] Offload flags fixes Maxime Coquelin

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