[dpdk-dev] [PATCH v4 7/8] virtio/lib:add virtio guest offload capabilities

[Liu, Jijiang]

Hi Qian,


> 
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Liu, Jijiang
> Sent: Wednesday, November 11, 2015 4:53 PM
> To: Yuanhan Liu
> Cc: dev at dpdk.org; Michael S. Tsirkin
> Subject: Re: [dpdk-dev] [PATCH v4 7/8] virtio/lib:add virtio guest offload
> capabilities
> 
> 
> 
> > -----Original Message-----
> > From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com]
> > Sent: Wednesday, November 11, 2015 4:44 PM
> > To: Liu, Jijiang
> > Cc: Michael S. Tsirkin; dev at dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH v4 7/8] virtio/lib:add virtio guest
> > offload capabilities
> >
> > On Wed, Nov 11, 2015 at 08:38:29AM +0000, Liu, Jijiang wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com]
> > > > Sent: Wednesday, November 11, 2015 4:31 PM
> > > > To: Liu, Jijiang; Michael S. Tsirkin
> > > > Cc: dev at dpdk.org
> > > > Subject: Re: [dpdk-dev] [PATCH v4 7/8] virtio/lib:add virtio guest
> > > > offload capabilities
> > > >
> > > > I don't think we need that, and it might be wrong to set those
> > > > fields at
> > vhost.
> > > >
> > > > And, TBH, I am not 100% sure that I understand what those flags
> > > > truely are and for. All I know is that they seem have something to
> > > > do with QEMU/TAP device.
> > >
> > > According to virtio standard, those fileds should be set.
> >
> > If so, you'd better quote them here, or even to your patch commit.
> 
> In the Virtual I/O Device (VIRTIO) Version 1.0 Committee Specification 02,
> 
> 
> [QIAN] Do we support virtio 1.0 in the vhost offload case? Currently it's virtio
> 0.95 Spec that we are testing.
> 
There are almost same description in  0.95 Spec,

(1)VIRTIO_NET_F_GUEST_CSUM (1) Guest handles packets with
partial checksum
(2) If the VIRTIO_NET_F_GUEST_CSUM feature was negotiated, the
VIRTIO_NET_HDR_F_NEEDS_CSUM bit in the ags eld may be
set: if so, the checksum on the packet is incomplete and the csum_start
and csum_oset elds indicate how to calculate it (see 1).

(3) The converse features are also available: a driver can save the virtual device
some work by negotiating these features.8 The VIRTIO_NET_F_GUEST_CSUM
feature indicates that partially checksummed packets can be received,
and if it can do that then the VIRTIO_NET_F_GUEST_TSO4, VIRTIO_
NET_F_GUEST_TSO6, VIRTIO_NET_F_GUEST_UFO and
VIRTIO_NET_F_GUEST_ECN are the input equivalents of the features
described above. See Receiving Packets below.