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From: "Ma, WenwuX" <wenwux.ma@intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	"Xia, Chenbo" <chenbo.xia@intel.com>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	"Matz, Olivier" <olivier.matz@6wind.com>
Cc: "stable@dpdk.org" <stable@dpdk.org>
Subject: RE: [PATCH 6/6] net/vhost: perform SW checksum in Tx path
Date: Thu, 9 Jun 2022 01:03:43 +0000
Message-ID: <SA0PR11MB45262E9095796CB2929BD1E4EBA79@SA0PR11MB4526.namprd11.prod.outlook.com> (raw)
In-Reply-To: <e8c43169-55b7-b8ad-2f5e-68fc95f1829d@redhat.com>



> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: 2022年6月8日 16:14
> To: Ma, WenwuX <wenwux.ma@intel.com>; dev@dpdk.org;
> jasowang@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>;
> david.marchand@redhat.com; Matz, Olivier <olivier.matz@6wind.com>
> Cc: stable@dpdk.org
> Subject: Re: [PATCH 6/6] net/vhost: perform SW checksum in Tx path
> 
> Hi Wenwu,
> 
> On 6/6/22 11:44, Ma, WenwuX wrote:
> >
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> >> Sent: 2022年6月2日 17:07
> >> To: Ma, WenwuX <wenwux.ma@intel.com>; dev@dpdk.org;
> >> jasowang@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>;
> >> david.marchand@redhat.com; Matz, Olivier <olivier.matz@6wind.com>
> >> Cc: stable@dpdk.org
> >> Subject: Re: [PATCH 6/6] net/vhost: perform SW checksum in Tx path
> >>
> >> Hi Wenwu,
> >>
> >> Sorry, I missed your review.
> >>
> >> On 5/7/22 05:20, Ma, WenwuX wrote:
> >>>
> >>>> -----Original Message-----
> >>>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> >>>> Sent: 2022年5月5日 18:27
> >>>> To: dev@dpdk.org; jasowang@redhat.com; Xia, Chenbo
> >>>> <chenbo.xia@intel.com>; david.marchand@redhat.com;
> >>>> olivier.matz@6wind.com
> >>>> Cc: stable@dpdk.org; Maxime Coquelin
> <maxime.coquelin@redhat.com>
> >>>> Subject: [PATCH 6/6] net/vhost: perform SW checksum in Tx path
> >>>>
> >>>> Virtio specification supports guest checksum offloading for L4,
> >>>> which is enabled with VIRTIO_NET_F_GUEST_CSUM feature
> negotiation.
> >> However,
> >>>> the Vhost PMD does not advertise Tx checksum offload capabilities.
> >>>>
> >>>> Advertising these offload capabilities at the ethdev level is not
> >>>> enough, because we could still end-up with the application enabling
> >>>> these offloads while the guest not negotiating it.
> >>>>
> >>>> This patch advertizes the Tx checksum offload capabilities, and
> >>>> introduces a compatibility layer to cover the case
> >>>> VIRTIO_NET_F_GUEST_CSUM has not been negotiated but the
> >> application
> >>>> does configure the Tx checksum offloads. This function performs the
> >>>> L4 Tx
> >> checksum in SW for UDP and TCP.
> >>>> Compared to Rx SW checksum, the Tx SW checksum function needs to
> >>>> compute the pseudo-header checksum, as we cannot knwo whether it
> >> was
> >>>> done before.
> >>>>
> >>>> This patch does not advertize SCTP checksum offloading capability
> >>>> for now, but it could be handled later if the need arises.
> >>>
> >>> In virtio_enqueue_offload(), if RTE_MBUF_F_TX_IP_CKSUM is set, we
> >>> will performs the L3 Tx checksum, why do not we advertise IPV4
> >>> checksum
> >> offloading capability?
> >>> Will we advertise it later?
> >>>
> >>
> >> Indeed, we have an IPv4 SW checksum fallback in Vhost library.
> >> We could think about adding the capability, but that's not urgent I
> >> think. Do you have a use-case where it is needed?
> >>
> > The GRO/GSO library doesn't re-calculate IPv4 checksums for
> merged/fragmented packets, it will cause iperf in the vm to fail.
> 
> Can you please elaborate?
> 
> If we don't expose the IPv4 checksum availability, it would be done by the
> application using the Vhost PMD, so the result will be the same from the VM
> point of view. Am I missing something?
> 
Ok, it is not urgent.

> Thanks,
> Maxime
> 
> >> Regards,
> >> Maxime
> >


      reply	other threads:[~2022-06-09  1:03 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-05 10:27 [PATCH 0/6] Vhost checksum offload improvements Maxime Coquelin
2022-05-05 10:27 ` [PATCH 1/6] Revert "app/testpmd: modify mac in csum forwarding" Maxime Coquelin
2022-05-16 13:03   ` Xia, Chenbo
2022-05-17 15:24     ` Zhang, Yuying
2022-05-19 16:27   ` David Marchand
2022-05-05 10:27 ` [PATCH 2/6] vhost: fix missing enqueue pseudo-header calculation Maxime Coquelin
2022-05-16 13:24   ` Xia, Chenbo
2022-05-05 10:27 ` [PATCH 3/6] net/vhost: enable compliant offloading mode Maxime Coquelin
2022-05-16 13:26   ` Xia, Chenbo
2022-05-16 13:28     ` Maxime Coquelin
2022-05-16 13:39       ` Xia, Chenbo
2022-06-07  1:19         ` Ma, WenwuX
2022-06-08  8:19           ` Maxime Coquelin
2022-05-05 10:27 ` [PATCH 4/6] net/vhost: make VLAN stripping flag a boolean Maxime Coquelin
2022-05-16 13:27   ` Xia, Chenbo
2022-05-05 10:27 ` [PATCH 5/6] net/vhost: perform SW checksum in Rx path Maxime Coquelin
2022-05-05 10:27 ` [PATCH 6/6] net/vhost: perform SW checksum in Tx path Maxime Coquelin
2022-05-07  3:20   ` Ma, WenwuX
2022-06-02  9:07     ` Maxime Coquelin
2022-06-06  9:44       ` Ma, WenwuX
2022-06-08  8:14         ` Maxime Coquelin
2022-06-09  1:03           ` Ma, WenwuX [this message]

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