9.3-RELEASE still instapanics on multi-mps(4) servers

[wollman at bimajority.org]

A good long while ago, I wrote:

>>>> I have two test servers now.  9.3 works just fine on one of them,
>>>> and panics on the other.  The one it works on is slightly older,
>>>> and has an mpt(4) controller for the boot drives, as opposed to
>>>> the system where the panic happens, which is mps(4)-only.  Both
>>>> systems have two SAS2116 controllers for external drives; the
>>>> ones on the working system have drives attached, and the ones on
>>>> the non-working system are not connected to anything (and in fact
>>>> disabled in the BIOS for now).

With the help of Stephen Mcconnell at Avago, I was eventually able to
pinpoint the issue.  The SAS enclosure device for the chassis hot-swap
backplane was being reported by the firmware as being in "slot 255",
which is impossible.  Updating the firmware (to "phase 19", the latest
released by Avago) and the MPT2 BIOS fixed the problem, and as a
bonus, the enclosure device is now properly recognized (which it
wasn't under 9.2).  There is undoubtedly still a bug in the driver
(both the "phase 16" driver in 9.3 and the "phase 19" driver that
Avago distributes), but since a firmware upgrade fixes it on my test
machine, I'm not going to put any more effort into finding it.

Now I just have to schedule some downtime for upgrading the three
production machines.

-GAWollman