netdev - Re: [PATCH] net: fec: Fixed panic problem with non-tso

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Message-ID: <1484713283.13165.89.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 17 Jan 2017 20:21:23 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "Ashizuka, Yuusuke" <ashiduka@...fujitsu.com>
Cc:     Andy Duan <fugang.duan@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: fec: Fixed panic problem with non-tso

On Wed, 2017-01-18 at 03:12 +0000, Ashizuka, Yuusuke wrote:

> indeed.
> 
> In the case of TSO with i.MX6 system (highmem enabled) with 2GB memory,
> "this_frag->page.p" did not become highmem area.
> (We confirmed by transferring about 100MB of files)
> 
> However, in the case of non-tso on an i.MX6 system with 2GB of memory,
> "this_frag->page.p" may become a highmem area.
> (Occurred with approximately 2MB of file transfer)
> 
> For non-tso only, I do not know the reason why "this_frag-> page.p" 
> in this driver shows highmem area.

This worries me, since this driver does not set NETIF_F_HIGHDMA in its
features.

No packet should be given to this driver with a highmem fragment

Check is done in illegal_highdma() in net/core/dev.c