RE: Intel i8xx watchdog driver

From: Don Bowman (don_at_sandvine.com)
Date: 03/25/04

  • Next message: Roman Kurakin: "[Fwd: [Fwd: Re: ATA/CHS problem]]" 
    To: 'Doug Ambrisko' <ambrisko@ambrisko.com>, Don Bowman <don@sandvine.com>
Date: Thu, 25 Mar 2004 17:40:33 -0500

    From: Doug Ambrisko [mailto:ambrisko@ambrisko.com]
    > Don Bowman writes:
    > | The Intel ICH3 (and probably all) has the feature it can
    > | issue an SMI on first count-down to 0, then a hard reset
    > | on 2nd. What we did was implement an SMM handler (in bios)
    > | that, when called due to watchdog, issued an NMI and did
    > | a return from smm.
    > | In FreeBSD, an NMI handler caught this (sometimes :),
    > | poke around to send a bit of data out to serial, moved the
    > | timer to the maximum value without reseting it, and then
    > | called panic [after mucking with cpl etc to pretend to
    > | own all locks :]
    > | If the NMI handler didn't get run, the hardware counted
    > | to 0 again and reset.
    > | If the NMI handler did get run, and then wedged somehow
    > | in the panic or whatever, the hardware counted to 0,
    > | and the system reset.
    > | If all worked well, you got a core, but at a minimum
    > | the system reset, and usually you got at least the
    > | serial output of some of the 'why'.
    > |
    > | The SMI is non-maskable (and higher priority than NMI).
    >
    > That sounds pretty cool. There was some bits in the ICH that
    > prevented an NMI to get to the CPU unless set a certain way.
    > I was generating an NMI via the PCI but. BTW you can do the
    > paper clip trick on PCI. The ICH seemed to be only one shot so
    > it de-bounced it. I could get multiple on a CPU NMI pin.
    >
    > How hard is to setup and trap SMI via a FreeBSD only solution?
    >
    > I haven't really looked much at that area but sounds useful.
    >
    > Doug A.
    >

    SMI under freebsd? Ha ha... Good luck! It didn't look very
    easy. The SMM, for those who don't know it, is a virtual
    86, real-mode thing, at a location in ram which is locked
    and unaccessible unless you are in smm mode :) If you
    are lucky, your bios didn't lock you out of it.

    there's an NMI_NOW in the ICH which can be used to
    programmatically cause an NMI. Some systems route this
    funny when in SMP mode... [ie nowhere???]. Some systems
    may have problems with this and the jumper/button
    for generating NMI.

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