Re: intermittant petabyte usage reported with broadcom nic

[Andi Kleen <andi@firstfloor.org>]

Roland Dreier <rdreier@cisco.com> writes:

> [Adding Michael Chan, who seems to look after bnx2, to the cc list]
> 
>  > To clarify it's an Intel Dual Core Xeon (I just wound up as thinking of
>  > them all as amd64s). Network card driver in use is the one defined by
>  > CONFIG_BNX2. Kernel's monolithic.
> 
> From a quick look at bnx2.c, it seems that the driver gives the NIC
> (firmware?) a block of memory to DMA stats into, and just reads from
> that memory in its get_stats method.  So if you're seeing wonky stats
> from the NIC intermittently, my best guess would be that firmware is
> occasionally writing junk into the stats block.

When only the firmware is writing to that area it could be put
into an own page and then write protected with change_page_attr()
That would catch any corruption coming from the rest of the kernel.

-Andi