linux-kernel - Re: [PATCH] net: don't use kvzalloc for DMA memory

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Message-ID: <alpine.LRH.2.02.1804181350050.17942@file01.intranet.prod.int.rdu2.redhat.com>
Date:   Wed, 18 Apr 2018 13:53:59 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     David Miller <davem@...emloft.net>
cc:     eric.dumazet@...il.com, edumazet@...gle.com,
        bhutchings@...arflare.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] net: don't use kvzalloc for DMA memory



On Wed, 18 Apr 2018, David Miller wrote:

> From: Mikulas Patocka <mpatocka@...hat.com>
> Date: Wed, 18 Apr 2018 12:44:25 -0400 (EDT)
> 
> > The structure net_device is followed by arbitrary driver-specific data 
> > (accessible with the function netdev_priv). And for virtio-net, these 
> > driver-specific data must be in DMA memory.
> 
> And we are saying that this assumption is wrong and needs to be
> corrected.

So, try to find all the networking drivers that to DMA to the private 
area.

The problem here is that kvzalloc usually returns DMA-able area, but it 
may return non-DMA area rarely, if the memory is too fragmented. So, we 
are in a situation, where some networking drivers will randomly fail. Go 
and find them.

Mikulas