Date: Fri, 7 Feb 2014 08:41:22 -0800 From: John-Mark Gurney <jmg@funkthat.com> To: Viktor <vpenkoff@gmail.com> Cc: freebsd-drivers@freebsd.org Subject: Re: Receiving jumbo frames Message-ID: <20140207164122.GE89104@funkthat.com> In-Reply-To: <52F49D36.8000103@gmail.com> References: <52F49D36.8000103@gmail.com>
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Viktor wrote this message on Fri, Feb 07, 2014 at 10:45 +0200:
> Hi, folks! I'm writing an extension functionality to not-yet published
> network driver.
> I'm receiving the typical ethernet frames without problems. Considering
> the datasheet of the device,
> I'm capable of receiving jumbo frames. When I try to do that, e.g. to
> send jumbo frame of 8000 bytes, I'm receiving only a limited count of
> them - 105, then the kernel crashes with the following message:
> "panic: vm_fault: fault on nofault entry, addr: cfcec000".
This happens when you access an address in kmem (kernel space) that
no longer has a page mapped... This is probably due to a pointer
that was previously valid, but then you aren't suppose to have and the
kernel unmapped the page because the subsystem free'd it...
> I have inspected a kernel dump with kgdb and the problem occurs at the
> function bus_dmamap_sync.
What part of this? It could be that you are trying to _sync a buffer
that doesn't belong to you anymore...
Are you making sure that you allocate new frames to replace them in the
receive buffer?
> Some background information:
> To enable the jumbo frame, one must set the appropriate register.
> At the software level, a ring buffer with the descriptors is implemented.
> The device, under which the driver runs, is arm-based.
> The freebsd version is 8.0. The device uses SerialDMA queues for
> transmitting and receiving.
> To receive packets, the CPU must perform the following:
> 1. Prepare a linked list of descriptors
> 2. Configure a given queue with the address of the first descriptor
> in the list,
> 3. enable SerialDMA;
>
> With the transmission - I don't have any problems. The logic is the same
> as by the reception of packets - ring buffer with descriptors.
>
> Any ideas what can cause this type of crashes?
With out better idea of what the driver is doing, or a line on which
the panic happens, the above is about all I can think of...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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