Subject: [RFC PATCH v2 00/10] fadump: Firmware-assisted dump support for Powerpc.
Date: Thursday 29th September 2011 15:02:46 UTC (over 5 years ago)
Hi All, Please find the version 2 of the patchset that implements firmware-assisted dump mechanism to capture kernel crash dump for Powerpc architecture. The firmware-assisted dump is a robust mechanism to get reliable kernel crash dump with assistance from firmware. This approach does not use kexec, instead firmware assists in booting the kdump kernel while preserving memory contents. Changes in v2: ------------- patch 01/10: - Modified the documentation to reflect the change of fadump_region file under debugfs filesystem. patch 02/10: - Modified to use standard pr_debug() macro. - Modified early_init_dt_scan_fw_dump() to get the size of "ibm,configure-kernel-dump-sizes" property and use it to iterate through an array of dump sections. - Introduced boot option 'fadump_reserve_mem=' to let user specify the fadump boot memory to be reserved. patch 03/10: - Removed few debug print statements. - Moved the setup_fadump() call from setup_system() and now calling it subsys_initcall. - Moved fadump_region attribute under debugfs. - Clear the TCE entries if firmware assisted dump is active. patch 05/10: - Moved the crash_fadump() invocation from generic code to panic notifier. - Introduced cpu_notes_buf_alloc() function to allocate cpu notes buffer using get_free_pages(). patch 08/10: - Introduced cpu_notes_buf_free() function to free memory allocated for cpu notes buffer. The most of the code implementation has been adapted from phyp assisted dump implementation written by Linas Vepstas and Manish Ahuja. The first patch is a documentation that talks about firmware-assisted dump mechanism, implementation details and TODO list. One of the important item from TODO list where I am looking forward for more ideas/suggestions is regarding fadump crash info structure in the scratch area before the ELF core header (see patch 4/10 and 5/10). The idea of introducing this structure is to pass some important crash info data to the second kernel which will help second kernel to populate ELF core header with correct data before it gets exported through /proc/vmcore. The current design implementation does not address the possibility of introducing additional fields (in future) to this structure without affecting compatibility. Following are the possible approaches I have in mind: 1. Introduce version field for version tracking, bump up the version whenever a new field is added to the structure in future. The version field can be used to find out what fields are valid for the current version of the structure. 2. Reserve the area of predefined size (say PAGE_SIZE) for this structure and have unused area as reserved (initialized to zero) for future field additions. The advantage of the approach 1 over 2 is, we don't need to reserve extra space. Please let me know if there is better solution available. I have tested the patches on following system configuration: 1. LPAR on Power6 with 4GB RAM and 8 CPUs 2. LPAR on Power7 with 2GB RAM and 20 CPUs 3. LPAR on Power7 with 1TB RAM and 896 CPUs These patches cleanly apply on commit 9e79e3e9 in linux-2.6 git tree. Please review the patchset and let me know your comments. Thanks, -Mahesh. --- Mahesh Salgaonkar (10): fadump: Add documentation for firmware-assisted dump. fadump: Reserve the memory for firmware assisted dump. fadump: Register for firmware assisted dump. fadump: Initialize elfcore header and add PT_LOAD program headers. fadump: Convert firmware-assisted cpu state dump data into elf notes. fadump: Add PT_NOTE program header for vmcoreinfo fadump: Introduce cleanup routine to invalidate /proc/vmcore. fadump: Invalidate registration and release reserved memory for general use. fadump: Invalidate the fadump registration during machine shutdown. fadump: Introduce config option for firmware assisted dump feature Documentation/powerpc/firmware-assisted-dump.txt | 237 ++++ arch/powerpc/Kconfig | 13 arch/powerpc/include/asm/fadump.h | 205 ++++ arch/powerpc/kernel/Makefile | 1 arch/powerpc/kernel/fadump.c | 1200 ++++++++++++++++++++++ arch/powerpc/kernel/iommu.c | 8 arch/powerpc/kernel/prom.c | 15 arch/powerpc/kernel/setup-common.c | 16 arch/powerpc/kernel/traps.c | 5 arch/powerpc/mm/hash_utils_64.c | 11 fs/proc/vmcore.c | 23 include/linux/crash_dump.h | 1 include/linux/memblock.h | 1 kernel/crash_dump.c | 33 + 14 files changed, 1767 insertions(+), 2 deletions(-) create mode 100644 Documentation/powerpc/firmware-assisted-dump.txt create mode 100644 arch/powerpc/include/asm/fadump.h create mode 100644 arch/powerpc/kernel/fadump.c -- Signature