[Simh] Raspberry Pi 3 with tun/tap causes XQ to fail

[Jeremy Begg]

Hi all,

>On Monday, November 13, 2017 at 2:04 AM, Jeremy Begg wrote:
>> I am trying to get SIMH up and running on the ethernet interface of a
>> Raspberry Pi 3.  I have followed the intructions in 0readme_ethernet.txt,
>> installing the libpcap-dev, bridge-utils and uml-utilities packages before
>> building SIMH itself.  I just ran 'make vax' and let it go, and the build to
>> completion.
>>
>> My problem is that I just can't get networking going.  To cut to the chase, if I
>> run the simulator without first setting up the br0 and tap0 interfaces, and
>> don't attempt to attach the XQ device, it works fine -- albeit without any
>> networking (as expected).
>>
>> If I configure SIMH to attach XQ directly to the Pi's eth0 interface (without
>> configuring br0/tap0) it works on the first run but fails selftest
>> 53 on the next run.  If I reboot the Pi and start the br0/tap0 interfaces and
>> then run the simulator the VAX console fails selftest 53 again.
>
>
>Hmm...  I've been trying to track down the 53 test failure, which I can't
>reproduce here.
>
>In general this should not have anything to do with the networking details
>you've got setup, but there might be some influence.

I think I have found the cause.  Yesterday Wilm pointed out that his
configuration did NOT require the tap0 interface to be assigned an IP
address by the host system, and Steve Mansfield-Device's blog is the
only place I've found that suggested this requirement.

It occurred to me after I reported it was working that I had in fact made
TWO changes: the successful boot did NOT connect the NVR.  Trying again just
now, with no IP address assigned to "tap0" and no NVR configured, the VAX
boots quite happily with a working network interface.

Mark, thank you for the detailed explanation about the failed selftest, but
I fear it's in vain.  I suspect it's just a corrupt NVR file instead.  So I
won't try the alternative ka655x.bin (unless you still think it might be
helpful to do so).

Regards,

	Jeremy Begg


>A little background explanation is warranted here.  Long ago, when the
>extended memory was added to the MicroVAX 3900 simulator (extending from
>64MB to 512MB), I had observed that boot ROM self test interval timer test
>intermittently failed (1 out of 10 times).  At the time, I attributed the
>failures to competing load on the host system while the timer test was
>running.  To avoid potential problem reports from users the interval timer
>tests were disabled with a patch to the ROM image.  The resulting KA655x.bin
>image was unmodified until this past January.  At that time, the timer
>related plumbing in simh was significantly reworked and it seemed like the
>ROM self tests should now pass without the need to side step them.  I
>re-enabled the tests and, in my testing I've run many hundreds of tests
>without failure, meanwhile there have been some reports like yours... :-(

>Since you've got a somewhat reproducible test 53 failure, will you please:

>1) send me the configuration file you're loading
>2) send me the ka655x.bin or ka655.bin file you may be loading in your configuration file
>3) explicitly load the attached ka655x.bin file prior to booting the simulator in your configuration file with:
>         sim> load -r ka655x_test.bin
>         sim> BOOT  (or BOOT CPU)
>4) let me know if you still can observe the self test problems you had previously seen.

>If the problem is completely solved, then I'll revise the packaged (and
>internal) ka655x.bin ROM image and these problems should be behind us.  If
>the problem persists, then I'll have to look for other ways to address it.

>Thanks.

>- Mark