netdev - Re: [PATCH net-next 07/13] virtio

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Message-ID: <CACGkMEuK3WEDYgeS+WvW-pb9NU01AXt1rxPQT0QsPgW4qu7h6Q@mail.gmail.com>
Date: Fri, 13 Sep 2024 11:22:31 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>, 
	Eugenio Pérez <eperezma@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, virtualization@...ts.linux.dev, 
	bpf@...r.kernel.org
Subject: Re: [PATCH net-next 07/13] virtio_net: refactor the xmit type

On Thu, Sep 12, 2024 at 3:54 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Wed, 11 Sep 2024 12:04:16 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Tue, Aug 20, 2024 at 3:33 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> > >
> > > Because the af-xdp will introduce a new xmit type, so I refactor the
> > > xmit type mechanism first.
> > >
> > > We use the last two bits of the pointer to distinguish the xmit type,
> > > so we can distinguish four xmit types. Now we have three types: skb,
> > > orphan and xdp.
> >
> > And if I was not wrong, we do not anymore use bitmasks. If yes, let's
> > explain the reason here.
>
> In general, pointers are aligned to 4 or 8 bytes. If it is aligned to 4 bytes,
> then only two bits are free for a pointer. So we can only use two bits.
>
> But there are 4 types here, so we can't use bits to distinguish them.
>
> b00 for skb
> b01 for SKB_ORPHAN
> b10 for XDP
> b11 for af-xdp tx

Let's add these in the changelog.

Thanks