netdev - Re: [PATCH net-next 10/10] nfp: nfdk: implement xdp tx path for NFDK

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Message-ID: <20220319031529.GA22805@nj-rack01-04.nji.corigine.com>
Date:   Sat, 19 Mar 2022 11:15:29 +0800
From:   Yinjun Zhang <yinjun.zhang@...igine.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Simon Horman <simon.horman@...igine.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        oss-drivers@...igine.com
Subject: Re: [PATCH net-next 10/10] nfp: nfdk: implement xdp tx path for NFDK

On Sat, Mar 19, 2022 at 09:55:46AM +0800, Yinjun Zhang wrote:
> On Fri, Mar 18, 2022 at 10:56:45AM -0700, Jakub Kicinski wrote:
> > On Fri, 18 Mar 2022 11:13:02 +0100 Simon Horman wrote:
> > > From: Yinjun Zhang <yinjun.zhang@...igine.com>
> > > 
> > > Due to the different definition of txbuf in NFDK comparing to NFD3,
> > > there're no pre-allocated txbufs for xdp use in NFDK's implementation,
> > > we just use the existed rxbuf and recycle it when xdp tx is completed.
> > > 
> > > For each packet to transmit in xdp path, we cannot use more than
> > > `NFDK_TX_DESC_PER_SIMPLE_PKT` txbufs, one is to stash virtual address,
> > > and another is for dma address, so currently the amount of transmitted
> > > bytes is not accumulated. Also we borrow the last bit of virtual addr
> > > to indicate a new transmitted packet due to address's alignment
> > > attribution.
> > > 
> > > Signed-off-by: Yinjun Zhang <yinjun.zhang@...igine.com>
> > > Signed-off-by: Fei Qin <fei.qin@...igine.com>
> > > Signed-off-by: Simon Horman <simon.horman@...igine.com>
> > 
> > Breaks 32 bit :(
> 
> You mean 32-bit arch? I'd thought of that, but why needn't
> `NFCT_PTRMASK` take that into account?

I see, because `nf_conn` is allocated from kmem_cache which is
created as 8 bytes aligned. I'll modify our implementation.