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

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Date:   Fri, 18 Mar 2022 21:30:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Yinjun Zhang <yinjun.zhang@...igine.com>
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, 19 Mar 2022 09:55:46 +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?

Simpler than that, I just meant the build.
It's about casting between 64b types and pointers:

drivers/net/ethernet/netronome/nfp/nfdk/dp.c: In function ‘nfp_nfdk_xdp_complete’:
drivers/net/ethernet/netronome/nfp/nfdk/dp.c:827:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  827 |                                      (void *)NFDK_TX_BUF_PTR(txbuf[0].raw),
      |                                      ^
drivers/net/ethernet/netronome/nfp/nfdk/dp.c: In function ‘nfp_nfdk_tx_xdp_buf’:
drivers/net/ethernet/netronome/nfp/nfdk/dp.c:909:24: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  909 |         txbuf[0].raw = (u64)rxbuf->frag | NFDK_TX_BUF_INFO_SOP;
      |                        ^