netdev - Re: [net-next, PATCH, v2] net: netsec: Sync dma for device on buffer allocation

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Message-Id: <20190705.154508.2238699627945877562.davem@davemloft.net>
Date:   Fri, 05 Jul 2019 15:45:08 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     ilias.apalodimas@...aro.org
Cc:     netdev@...r.kernel.org, jaswinder.singh@...aro.org,
        ard.biesheuvel@...aro.org, arnd@...db.de
Subject: Re: [net-next, PATCH, v2] net: netsec: Sync dma for device on
 buffer allocation

From: Ilias Apalodimas <ilias.apalodimas@...aro.org>
Date: Thu,  4 Jul 2019 17:46:09 +0300

> Quoting Arnd,
> 
> We have to do a sync_single_for_device /somewhere/ before the
> buffer is given to the device. On a non-cache-coherent machine with
> a write-back cache, there may be dirty cache lines that get written back
> after the device DMA's data into it (e.g. from a previous memset
> from before the buffer got freed), so you absolutely need to flush any
> dirty cache lines on it first.
> 
> Since the coherency is configurable in this device make sure we cover
> all configurations by explicitly syncing the allocated buffer for the
> device before refilling it's descriptors
> 
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> ---
> 
> Changes since V1: 
> - Make the code more readable

Ooops, I applied v1.  Could you please send me any changes still necessary
relative to that?

Thanks.