linux/kernel/crash_core.c, branch v6.17

kdump: wait for DMA to finish when using CMA

2025-07-20T02:08:23Z

When re-using the CMA area for kdump there is a risk of pending DMA into pinned user pages in the CMA area. Pages residing in CMA areas can usually not get long-term pinned and are instead migrated away from the CMA area, so long-term pinning is typically not a concern. (BUGs in the kernel might still lead to long-term pinning of such pages if everything goes wrong.) Pages pinned without FOLL_LONGTERM remain in the CMA and may possibly be the source or destination of a pending DMA transfer. Although there is no clear specification how long a page may be pinned without FOLL_LONGTERM, pinning without the flag shows an intent of the caller to only use the memory for short-lived DMA transfers, not a transfer initiated by a device asynchronously at a random time in the future. Add a delay of CMA_DMA_TIMEOUT_SEC seconds before starting the kdump kernel, giving such short-lived DMA transfers time to finish before the CMA memory is re-used by the kdump kernel. Set CMA_DMA_TIMEOUT_SEC to 10 seconds - chosen arbitrarily as both a huge margin for a DMA transfer, yet not increasing the kdump time too significantly. Link: https://lkml.kernel.org/r/aEqpgDIBndZ5LXSo@dwarf.suse.cz Signed-off-by: Jiri Bohac Acked-by: David Hildenbrand Cc: Baoquan He Cc: Dave Young Cc: Donald Dutile Cc: Michal Hocko Cc: Philipp Rudo Cc: Pingfan Liu Cc: Tao Liu Cc: Vivek Goyal Signed-off-by: Andrew Morton

crash: Use note name macros

2025-02-11T00:56:58Z

Use note name macros to match with the userspace's expectation. Signed-off-by: Akihiko Odaki Acked-by: Baoquan He Reviewed-by: Dave Martin Link: https://lore.kernel.org/r/20250115-elf-v5-4-0f9e55bbb2fc@daynix.com Signed-off-by: Kees Cook

kexec/crash: no crash update when kexec in progress

2024-11-06T01:12:27Z

The following errors are observed when kexec is done with SMT=off on powerpc. [ 358.458385] Removing IBM Power 842 compression device [ 374.795734] kexec_core: Starting new kernel [ 374.795748] kexec: Waking offline cpu 1. [ 374.875695] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 374.935833] kexec: Waking offline cpu 2. [ 375.015664] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate snip.. [ 375.515823] kexec: Waking offline cpu 6. [ 375.635667] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate [ 375.695836] kexec: Waking offline cpu 7. To avoid kexec kernel boot failure on PowerPC, all the present CPUs that are offline are brought online during kexec. For more information, refer to commit e8e5c2155b00 ("powerpc/kexec: Fix orphaned offline CPUs across kexec"). Bringing the CPUs online triggers the crash hotplug handler, crash_handle_hotplug_event(), to update the kdump image. Since the system is on the kexec kernel boot path and the kexec lock is held, the crash_handle_hotplug_event() function fails to acquire the same lock to update the kdump image, resulting in the error messages mentioned above. To fix this, return from crash_handle_hotplug_event() without printing the error message if kexec is in progress. The same applies to the crash_check_hotplug_support() function. Return 0 if kexec is in progress because kernel is not in a position to update the kdump image. Link: https://lkml.kernel.org/r/20240921103745.560430-1-sourabhjain@linux.ibm.com Signed-off-by: Sourabh Jain Acked-by: Baoquan he Reported-by: Sachin P Bappalige Cc: Hari Bathini Cc: Michael Ellerman Signed-off-by: Andrew Morton

Document/kexec: generalize crash hotplug description

2024-09-02T03:43:37Z

Commit 79365026f869 ("crash: add a new kexec flag for hotplug support") generalizes the crash hotplug support to allow architectures to update multiple kexec segments on CPU/Memory hotplug and not just elfcorehdr. Therefore, update the relevant kernel documentation to reflect the same. No functional change. Link: https://lkml.kernel.org/r/20240812041651.703156-1-sourabhjain@linux.ibm.com Signed-off-by: Sourabh Jain Reviewed-by: Petr Tesarik Acked-by: Baoquan He Cc: Hari Bathini Cc: Petr Tesarik Cc: Sourabh Jain Cc: Jonathan Corbet Signed-off-by: Andrew Morton

Merge tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-05-19T21:02:03Z

Pull non-mm updates from Andrew Morton: "Mainly singleton patches, documented in their respective changelogs. Notable series include: - Some maintenance and performance work for ocfs2 in Heming Zhao's series "improve write IO performance when fragmentation is high". - Some ocfs2 bugfixes from Su Yue in the series "ocfs2 bugs fixes exposed by fstests". - kfifo header rework from Andy Shevchenko in the series "kfifo: Clean up kfifo.h". - GDB script fixes from Florian Rommel in the series "scripts/gdb: Fixes for $lx_current and $lx_per_cpu". - After much discussion, a coding-style update from Barry Song explaining one reason why inline functions are preferred over macros. The series is "codingstyle: avoid unused parameters for a function-like macro"" * tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (62 commits) fs/proc: fix softlockup in __read_vmcore nilfs2: convert BUG_ON() in nilfs_finish_roll_forward() to WARN_ON() scripts: checkpatch: check unused parameters for function-like macro Documentation: coding-style: ask function-like macros to evaluate parameters nilfs2: use __field_struct() for a bitwise field selftests/kcmp: remove unused open mode nilfs2: remove calls to folio_set_error() and folio_clear_error() kernel/watchdog_perf.c: tidy up kerneldoc watchdog: allow nmi watchdog to use raw perf event watchdog: handle comma separated nmi_watchdog command line nilfs2: make superblock data array index computation sparse friendly squashfs: remove calls to set the folio error flag squashfs: convert squashfs_symlink_read_folio to use folio APIs scripts/gdb: fix detection of current CPU in KGDB scripts/gdb: make get_thread_info accept pointers scripts/gdb: fix parameter handling in $lx_per_cpu scripts/gdb: fix failing KGDB detection during probe kfifo: don't use "proxy" headers media: stih-cec: add missing io.h media: rc: add missing io.h ...

crash: add prefix for crash dumping messages

2024-05-08T15:41:26Z

Add pr_fmt() to kernel/crash_core.c to add the module name to debugging message printed as prefix. And also add prefix 'crashkernel:' to two lines of message printing code in kernel/crash_reserve.c. In kernel/crash_reserve.c, almost all debugging messages have 'crashkernel:' prefix or there's keyword crashkernel at the beginning or in the middle, adding pr_fmt() makes it redundant. Link: https://lkml.kernel.org/r/20240418035843.1562887-1-bhe@redhat.com Signed-off-by: Baoquan He Cc: Dave Young Cc: Jiri Slaby Signed-off-by: Andrew Morton

crash: add a new kexec flag for hotplug support

2024-04-23T04:59:01Z

Commit a72bbec70da2 ("crash: hotplug support for kexec_load()") introduced a new kexec flag, `KEXEC_UPDATE_ELFCOREHDR`. Kexec tool uses this flag to indicate to the kernel that it is safe to modify the elfcorehdr of the kdump image loaded using the kexec_load system call. However, it is possible that architectures may need to update kexec segments other then elfcorehdr. For example, FDT (Flatten Device Tree) on PowerPC. Introducing a new kexec flag for every new kexec segment may not be a good solution. Hence, a generic kexec flag bit, `KEXEC_CRASH_HOTPLUG_SUPPORT`, is introduced to share the CPU/Memory hotplug support intent between the kexec tool and the kernel for the kexec_load system call. Now we have two kexec flags that enables crash hotplug support for kexec_load system call. First is KEXEC_UPDATE_ELFCOREHDR (only used in x86), and second is KEXEC_CRASH_HOTPLUG_SUPPORT (for all architectures). To simplify the process of finding and reporting the crash hotplug support the following changes are introduced. 1. Define arch specific function to process the kexec flags and determine crash hotplug support 2. Rename the @update_elfcorehdr member of struct kimage to @hotplug_support and populate it for both kexec_load and kexec_file_load syscalls, because architecture can update more than one kexec segment 3. Let generic function crash_check_hotplug_support report hotplug support for loaded kdump image based on value of @hotplug_support To bring the x86 crash hotplug support in line with the above points, the following changes have been made: - Introduce the arch_crash_hotplug_support function to process kexec flags and determine crash hotplug support - Remove the arch_crash_hotplug_[cpu|memory]_support functions Signed-off-by: Sourabh Jain Acked-by: Baoquan He Acked-by: Hari Bathini Signed-off-by: Michael Ellerman Link: https://msgid.link/20240326055413.186534-3-sourabhjain@linux.ibm.com

crash: forward memory_notify arg to arch crash hotplug handler

2024-04-23T04:59:01Z

In the event of memory hotplug or online/offline events, the crash memory hotplug notifier `crash_memhp_notifier()` receives a `memory_notify` object but doesn't forward that object to the generic and architecture-specific crash hotplug handler. The `memory_notify` object contains the starting PFN (Page Frame Number) and the number of pages in the hot-removed memory. This information is necessary for architectures like PowerPC to update/recreate the kdump image, specifically `elfcorehdr`. So update the function signature of `crash_handle_hotplug_event()` and `arch_crash_handle_hotplug_event()` to accept the `memory_notify` object as an argument from crash memory hotplug notifier. Since no such object is available in the case of CPU hotplug event, the crash CPU hotplug notifier `crash_cpuhp_online()` passes NULL to the crash hotplug handler. Signed-off-by: Sourabh Jain Acked-by: Baoquan He Acked-by: Hari Bathini Signed-off-by: Michael Ellerman Link: https://msgid.link/20240326055413.186534-2-sourabhjain@linux.ibm.com

crash: split crash dumping code out from kexec_core.c

2024-02-24T01:48:22Z

Currently, KEXEC_CORE select CRASH_CORE automatically because crash codes need be built in to avoid compiling error when building kexec code even though the crash dumping functionality is not enabled. E.g -------------------- CONFIG_CRASH_CORE=y CONFIG_KEXEC_CORE=y CONFIG_KEXEC=y CONFIG_KEXEC_FILE=y --------------------- After splitting out crashkernel reservation code and vmcoreinfo exporting code, there's only crash related code left in kernel/crash_core.c. Now move crash related codes from kexec_core.c to crash_core.c and only build it in when CONFIG_CRASH_DUMP=y. And also wrap up crash codes inside CONFIG_CRASH_DUMP ifdeffery scope, or replace inappropriate CONFIG_KEXEC_CORE ifdef with CONFIG_CRASH_DUMP ifdef in generic kernel files. With these changes, crash_core codes are abstracted from kexec codes and can be disabled at all if only kexec reboot feature is wanted. Link: https://lkml.kernel.org/r/20240124051254.67105-5-bhe@redhat.com Signed-off-by: Baoquan He Cc: Al Viro Cc: Eric W. Biederman Cc: Hari Bathini Cc: Pingfan Liu Cc: Klara Modin Cc: Michael Kelley Cc: Nathan Chancellor Cc: Stephen Rothwell Cc: Yang Li Signed-off-by: Andrew Morton

crash: split vmcoreinfo exporting code out from crash_core.c

2024-02-24T01:48:22Z

Now move the relevant codes into separate files: kernel/crash_reserve.c, include/linux/crash_reserve.h. And add config item CRASH_RESERVE to control its enabling. And also update the old ifdeffery of CONFIG_CRASH_CORE, including of and config item dependency on CRASH_CORE accordingly. And also do renaming as follows: - arch/xxx/kernel/{crash_core.c => vmcore_info.c} because they are only related to vmcoreinfo exporting on x86, arm64, riscv. And also Remove config item CRASH_CORE, and rely on CONFIG_KEXEC_CORE to decide if build in crash_core.c. [yang.lee@linux.alibaba.com: remove duplicated include in vmcore_info.c] Link: https://lkml.kernel.org/r/20240126005744.16561-1-yang.lee@linux.alibaba.com Link: https://lkml.kernel.org/r/20240124051254.67105-3-bhe@redhat.com Signed-off-by: Baoquan He Signed-off-by: Yang Li Acked-by: Hari Bathini Cc: Al Viro Cc: Eric W. Biederman Cc: Pingfan Liu Cc: Klara Modin Cc: Michael Kelley Cc: Nathan Chancellor Cc: Stephen Rothwell Cc: Yang Li Signed-off-by: Andrew Morton