RFC purgatory: Add basic support for IPMI command execution

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. So, some enterprise users want to save minimal information befor booting the second kernel.

One of the approaches is to use panic notifier call or pstore feature. For example, a panic notifier callback registered by IPMI driver saves the panic message to BMC's SEL before booting the second kernel. Similarly, pstore saves kernel logs to a non-volatile memory on the server. However, since these functionalities run with crashed kernel, they may fail to complete their work and boot the second kernel.

So, another approach; saving minimal information to BMC's SEL in the purgatory. Since the purgatory code doesn't rely on the crashed kernel, we can run it safely after verifying the hash of the code.

This patch set is the first step to the final goal; it provides a basic support for IPMI command execution in purgatory. IPMI specification defines multiple interfaces to BMC, and this patch set uses one of them, KCS I/F, which talks with BMC via I/O port like keyboard controllers. As a use case for that, options to start/stop BMC's watchdog timer before booting the second kernel are also provided. These options are useful for the cases where:

- you want to automatically reboot the server when the second kernel hangs up while booting
- you want to prevent the second kernel from being stopped by the watchdog timer enabled while the first kernel is running

If the BMC doesn't work well, the IPMI command execution can take indefinite time and fail to boot the second kernel. To avoid this, timeout logic based on RTC polling is also implemented.

NOTE: This is an RFC version, so some parts are incomplete; these codes are unconditionally built into the kexec binary, and I/O ports for KCS I/F and timeout (5 seconds) are hard-coded, and etc.

Future plan:
Add an option to save the panic message and instruction pointers to BMC's SEL in purgatory. To realize this, we first need to pass the panic message to the purgatory. Instruction pointers are already passed to the second kernel through ELF notes, so just read them.

---

Hidehiro Kawai (4):
purgatory/ipmi: Support BMC watchdog timer start/stop in purgatory
purgatory: Introduce timeout API
purgatory/x86: Support CMOS RTC
purgatory/ipmi: Add timeout logic to IPMI command processing

 kexec/ipmi.h                   |    9 +
 kexec/kexec.c                  |   18 ++
 kexec/kexec.h                  |    6 +
 purgatory/Makefile             |    5 +
 purgatory/arch/i386/Makefile   |    1 
 purgatory/arch/i386/rtc_cmos.c |  104 ++++++++++++++
 purgatory/arch/x86_64/Makefile |    1 
 purgatory/include/purgatory.h  |    3 
 purgatory/include/time.h       |   33 +++++
 purgatory/ipmi.c               |  293 ++++++++++++++++++++++++++++++++++++++++
 purgatory/purgatory.c          |    4 +
 purgatory/time.c               |   58 ++++++++
 12 files changed, 533 insertions(+), 2 deletions(-)
 create mode 100644 kexec/ipmi.h
 create mode 100644 purgatory/arch/i386/rtc_cmos.c
 create mode 100644 purgatory/include/time.h
 create mode 100644 purgatory/ipmi.c
 create mode 100644 purgatory/time.c

Hidehiro Kawai
Hitachi, Ltd. Research & Development Group



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