[RFC v2 PATCH 0/7] purgatory: Say last words in kexec on panic case

[Hidehiro Kawai]

This is the version 2 of RFC patch series previously named
"purgatory: Add basic support for IPMI command execution."

Changes since RFC v1:
- Add --ipmi-kcs-ports option to specify I/O ports for KCS I/F
- Add --ipmi-handle-panic option to generate an event on BMC to
  inform and record about the panic
- Add --output-cpu-ip option to output IP registers to console
  and BMC's SEL
...and various cleanups and improvements

I performed some Web searches, and I found that major BMCs still
support KCS I/F.  Although this patch series supports only KCS I/F, it
should cover many recent servers with BMC.  However, I/O ports used
for KCS I/F are varies among servers, so I added an option to specify
port numbers for KCS.

About error handling for KCS protocol, I re-checked IPMI
specification, and I found that simply retrying on error is
sufficient.  So I didn't change the logic for the simplicity.  Please
see PATCH 3/7 for details.


Background and purpose
======================

If the second kernel for crash dumping hangs up while booting, no
information related to the first kernel will be saved.  This makes
crash cause analysis difficult.  Some enterprise users don't permit
the same faults happen multiple times, so we want to save minimal
information before booting the second kernel.


Approaches
==========

One of the approaches is (1) to use panic notifier call or kmsg dump
feature.  For example, a panic notifier callback registered by IPMI
driver can save the panic message to BMC's SEL before booting the
second kernel.  Similarly, kmsg dump saves kernel logs to a non-
volatile memory on the server.  This approach covers multiple
hardware/firmware implementation.  However, doing many things in
crashed kernel will reduce the reliability.  Additionally, a part of
the code is also used for normal operation and still evolving.  This
would makes it difficult to keep stable.

Another approach is (2) to save minimal information to BMC's SEL in
purgatory.  It is difficult to do complicate things in purgatory, but
fortunately IPMI specification defines a simple interface, KCS
(Keyboard Controller Style) I/F.  KCS is controlled by two I/O ports
and supported by most of major BMCs.

Here, we want more reliable one for the purpose, we adopt (2).


What are provided?
==================

This patch series provides multiple RAS features other than the main
purpose described above.

- Timeout mechanism relying on polling RTC
- API to access BMC via KCS I/F 
- Command line option to start/stop BMC's watchdog timer in purgatory
- Command line option to write the value of RIP registers to SEL and/or
  serial console (useful for kernel hang-up cases)
- Command line option to generate a plantform event on BMC (useful for
  server monitoring or HA clustering; you can make the BMC issue an
  SNMP trap)
- Command line option to change the default I/O ports of KCS I/F


Limitations of RFC version
==========================

This patch serires is incomplete, and there are some limitations.

- Related codes are unconditionally built into the kexec binary
- Implemented only for x86_64 (it may break the build for other
  architectures)
- Timeout value for IPMI operations is hard-coded


Future plan
===========

- Add an option to save the panic message to BMC's SEL (this requires
  some kernel modifications)

---

Hidehiro Kawai (7):
      purgatory: Introduce timeout API
      purgatory/x86: Support CMOS RTC
      purgatory/ipmi: Support IPMI KCS interface
      purgatory/ipmi: Support BMC watchdog timer start/stop in purgatory
      purgatory/ipmi: Add an option for purgatory to handle panic event with IPMI
      purgatory/x86: Add an option to output IP registers to console in panic case
      purgatory/ipmi/x86: Support logging of IP registers into SEL


 kexec/arch/i386/crashdump-x86.c              |   10 -
 kexec/arch/i386/include/arch/options.h       |    4 
 kexec/arch/i386/kexec-x86.h                  |    1 
 kexec/arch/x86_64/kexec-x86_64.c             |   15 +
 kexec/ipmi.h                                 |    9 +
 kexec/kexec.c                                |   51 ++++
 kexec/kexec.h                                |   11 +
 purgatory/Makefile                           |    6 
 purgatory/arch/i386/Makefile                 |    1 
 purgatory/arch/i386/purgatory-x86.h          |    2 
 purgatory/arch/i386/rtc_cmos.c               |  107 ++++++++
 purgatory/arch/x86_64/Makefile               |    2 
 purgatory/arch/x86_64/purgatory-elf-x86_64.c |   82 ++++++
 purgatory/arch/x86_64/purgatory-x86_64.c     |   35 ++-
 purgatory/include/purgatory-elf.h            |   13 +
 purgatory/include/purgatory.h                |    9 +
 purgatory/include/time.h                     |   33 ++
 purgatory/ipmi.c                             |  361 ++++++++++++++++++++++++++
 purgatory/purgatory-elf-core.c               |   64 +++++
 purgatory/time.c                             |   59 ++++
 20 files changed, 866 insertions(+), 9 deletions(-)
 create mode 100644 kexec/ipmi.h
 create mode 100644 purgatory/arch/i386/rtc_cmos.c
 create mode 100644 purgatory/arch/x86_64/purgatory-elf-x86_64.c
 create mode 100644 purgatory/include/purgatory-elf.h
 create mode 100644 purgatory/include/time.h
 create mode 100644 purgatory/ipmi.c
 create mode 100644 purgatory/purgatory-elf-core.c
 create mode 100644 purgatory/time.c


-- 
Hidehiro Kawai
Hitachi, Ltd. Research & Development Group