netdev - Re: [PATCH] net: netsec: Correct dma sync for XDP

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Date:   Thu, 17 Oct 2019 09:49:31 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, jaswinder.singh@...aro.org,
        davem@...emloft.net, brouer@...hat.com, lorenzo@...nel.org
Subject: Re: [PATCH] net: netsec: Correct dma sync for XDP_TX frames

Hi Jakub, 

On Wed, Oct 16, 2019 at 05:14:01PM -0700, Jakub Kicinski wrote:
> On Wed, 16 Oct 2019 14:40:32 +0300, Ilias Apalodimas wrote:
> > bpf_xdp_adjust_head() can change the frame boundaries. Account for the
> > potential shift properly by calculating the new offset before
> > syncing the buffer to the device for XDP_TX
> > 
> > Fixes: ba2b232108d3 ("net: netsec: add XDP support")
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> 
> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> 
> You should target this to the bpf or net tree (appropriate [PATCH xyz]
> marking). Although I must admit it's unclear to me as well whether the
> driver changes should be picked up by bpf maintainers or Dave :S

My bad i forgot to add the net-next tag. I'd prefer Dave picking that up, since
he picked all the XDP-related patches for this driver before. 
Dave shall i re-send with the proper tag?

> 
> > diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
> > index f9e6744d8fd6..41ddd8fff2a7 100644
> > --- a/drivers/net/ethernet/socionext/netsec.c
> > +++ b/drivers/net/ethernet/socionext/netsec.c
> > @@ -847,8 +847,8 @@ static u32 netsec_xdp_queue_one(struct netsec_priv *priv,
> >  		enum dma_data_direction dma_dir =
> >  			page_pool_get_dma_dir(rx_ring->page_pool);
> >  
> > -		dma_handle = page_pool_get_dma_addr(page) +
> > -			NETSEC_RXBUF_HEADROOM;
> > +		dma_handle = page_pool_get_dma_addr(page) + xdpf->headroom +
> > +			sizeof(*xdpf);
> 
> very nitpick: I'd personally write addr + sizeof(*xdpf) + xdpf->headroom
> since that's the order in which they appear in memory
> 
> But likely not worth reposting for just that :)

Isn't sizeof static anyway? If Dave needs a v2 with the proper tag i'll change
this as well 

> 
> >  		dma_sync_single_for_device(priv->dev, dma_handle, xdpf->len,
> >  					   dma_dir);
> >  		tx_desc.buf_type = TYPE_NETSEC_XDP_TX;
> 

Thanks
/Ilias