kernel/linux.git/arch/powerpc/include/asm/kexec.h, branch linux-7.0.y

powerpc/crash: Update backup region offset in elfcorehdr on memory hotplug

2026-05-23T11:08:35+00:00

[ Upstream commit f53b24d1fa263f56155213eabab734c18d884aff ] When elfcorehdr is prepared for kdump, the program header representing the first 64 KB of memory is expected to have its offset point to the backup region. This is required because purgatory copies the first 64 KB of the crashed kernel memory to this backup region following a kernel crash. This allows the capture kernel to use the first 64 KB of memory to place the exception vectors and other required data. When elfcorehdr is recreated due to memory hotplug, the offset of the program header representing the first 64 KB is not updated. As a result, the capture kernel exports the first 64 KB at offset 0, even though the data actually resides in the backup region. Fix this by calling sync_backup_region_phdr() to update the program header offset in the elfcorehdr created during memory hotplug. sync_backup_region_phdr() works for images loaded via the kexec_file_load syscall. However, it does not work for kexec_load, because image->arch.backup_start is not initialized in that case. So introduce machine_kexec_post_load() to process the elfcorehdr prepared by kexec-tools and initialize image->arch.backup_start for kdump images loaded via kexec_load syscall. Rename update_backup_region_phdr() to sync_backup_region_phdr() and extend it to synchronize the backup region offset between the kdump image and the ELF core header. The helper now supports updating either the kdump image from the ELF program header or updating the ELF program header from the kdump image, avoiding code duplication. Define ARCH_HAS_KIMAGE_ARCH and struct kimage_arch when CONFIG_KEXEC_FILE or CONFIG_CRASH_DUMP is enabled so that kimage->arch.backup_start is available with the kexec_load system call. This patch depends on the patch titled "powerpc/crash: fix backup region offset update to elfcorehdr". Fixes: 849599b702ef ("powerpc/crash: add crash memory hotplug support") Reviewed-by: Aditya Gupta Signed-off-by: Sourabh Jain Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260312083051.1935737-3-sourabhjain@linux.ibm.com Signed-off-by: Sasha Levin

powerpc/kdump: Add support for crashkernel CMA reservation

2025-11-11T08:41:08+00:00

Commit 35c18f2933c5 ("Add a new optional ",cma" suffix to the crashkernel= command line option") and commit ab475510e042 ("kdump: implement reserve_crashkernel_cma") added CMA support for kdump crashkernel reservation. Extend crashkernel CMA reservation support to powerpc. The following changes are made to enable CMA reservation on powerpc: - Parse and obtain the CMA reservation size along with other crashkernel parameters - Call reserve_crashkernel_cma() to allocate the CMA region for kdump - Include the CMA-reserved ranges in the usable memory ranges for the kdump kernel to use. - Exclude the CMA-reserved ranges from the crash kernel memory to prevent them from being exported through /proc/vmcore. With the introduction of the CMA crashkernel regions, crash_exclude_mem_range() needs to be called multiple times to exclude both crashk_res and crashk_cma_ranges from the crash memory ranges. To avoid repetitive logic for validating mem_ranges size and handling reallocation when required, this functionality is moved to a new wrapper function crash_exclude_mem_range_guarded(). To ensure proper CMA reservation, reserve_crashkernel_cma() is called after pageblock_order is initialized. Update kernel-parameters.txt to document CMA support for crashkernel on powerpc architecture. Signed-off-by: Sourabh Jain Reviewed-by: Ritesh Harjani (IBM) Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20251107080334.708028-1-sourabhjain@linux.ibm.com

powerpc: Replace ASSEMBLY with ASSEMBLER in non-uapi headers

2025-09-01T07:53:29+00:00

While the GCC and Clang compilers already define __ASSEMBLER__ automatically when compiling assembler code, __ASSEMBLY__ is a macro that only gets defined by the Makefiles in the kernel. This is bad since macros starting with two underscores are names that are reserved by the C language. It can also be very confusing for the developers when switching between userspace and kernelspace coding, or when dealing with uapi headers that rather should use __ASSEMBLER__ instead. So let's standardize now on the __ASSEMBLER__ macro that is provided by the compilers. This is almost a completely mechanical patch (done with a simple "sed -i" statement), apart from tweaking two comments manually in arch/powerpc/include/asm/bug.h and arch/powerpc/include/asm/kasan.h (which did not have proper underscores at the end) and fixing a checkpatch error about spaces in arch/powerpc/include/asm/spu_csa.h. Signed-off-by: Thomas Huth Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20250801082007.32904-3-thuth@redhat.com

powerpc/crash: use generic crashkernel reservation

2025-03-17T05:30:48+00:00

Commit 0ab97169aa05 ("crash_core: add generic function to do reservation") added a generic function to reserve crashkernel memory. So let's use the same function on powerpc and remove the architecture-specific code that essentially does the same thing. The generic crashkernel reservation also provides a way to split the crashkernel reservation into high and low memory reservations, which can be enabled for powerpc in the future. Along with moving to the generic crashkernel reservation, the code related to finding the base address for the crashkernel has been separated into its own function name get_crash_base() for better readability and maintainability. Link: https://lkml.kernel.org/r/20250131113830.925179-8-sourabhjain@linux.ibm.com Signed-off-by: Sourabh Jain Reviewed-by: Mahesh Salgaonkar Acked-by: Hari Bathini Cc: Baoquan he Cc: Madhavan Srinivasan Cc: Michael Ellerman Signed-off-by: Andrew Morton

powerpc/crash: use generic APIs to locate memory hole for kdump

2025-03-17T05:30:48+00:00

On PowerPC, the memory reserved for the crashkernel can contain components like RTAS, TCE, OPAL, etc., which should be avoided when loading kexec segments into crashkernel memory. Due to these special components, PowerPC has its own set of APIs to locate holes in the crashkernel memory for loading kexec segments for kdump. However, for loading kexec segments in the kexec case, PowerPC already uses generic APIs to locate holes. The previous patch in this series, titled "crash: Let arch decide usable memory range in reserved area," introduced arch-specific hook to handle such special regions in the crashkernel area. So, switch PowerPC to use the generic APIs to locate memory holes for kdump and remove the redundant PowerPC-specific APIs. Link: https://lkml.kernel.org/r/20250131113830.925179-5-sourabhjain@linux.ibm.com Signed-off-by: Sourabh Jain Cc: Baoquan he Cc: Hari Bathini Cc: Madhavan Srinivasan Cc: Mahesh Salgaonkar Cc: Michael Ellerman Signed-off-by: Andrew Morton

kexec: Consolidate machine_kexec_mask_interrupts() implementation

2024-12-11T19:32:34+00:00

Consolidate the machine_kexec_mask_interrupts implementation into a common function located in a new file: kernel/irq/kexec.c. This removes duplicate implementations from architecture-specific files in arch/arm, arch/arm64, arch/powerpc, and arch/riscv, reducing code duplication and improving maintainability. The new implementation retains architecture-specific behavior for CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD, which was previously implemented for ARM64. When enabled (currently for ARM64), it clears the active state of interrupts forwarded to virtual machines (VMs) before handling other interrupt masking operations. Signed-off-by: Eliav Farber Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241204142003.32859-2-farbere@amazon.com

powerpc/kexec_file: fix extra size calculation for kexec FDT

2024-06-17T12:48:45+00:00

While setting up the FDT for kexec, CPU nodes that are added after the system boots and reserved memory ranges are incorporated into the initial_boot_params (base FDT). However, they are not taken into account when determining the additional size needed for the kexec FDT. As a result, kexec fails to load, generating the following error: [1116.774451] Error updating memory reserve map: FDT_ERR_NOSPACE kexec_file_load failed: No such process Therefore, consider the extra size for CPU nodes added post-system boot and reserved memory ranges while preparing the kexec FDT. While adding a new parameter to the setup_new_fdt_ppc64 function, it was noticed that there were a couple of unused parameters, so they were removed. Signed-off-by: Sourabh Jain Signed-off-by: Michael Ellerman Link: https://msgid.link/20240510102235.2269496-2-sourabhjain@linux.ibm.com

powerpc/crash: add crash memory hotplug support

2024-04-23T05:00:04+00:00

Extend the arch crash hotplug handler, as introduced by the patch title ("powerpc: add crash CPU hotplug support"), to also support memory add/remove events. Elfcorehdr describes the memory of the crash kernel to capture the kernel; hence, it needs to be updated if memory resources change due to memory add/remove events. Therefore, arch_crash_handle_hotplug_event() is updated to recreate the elfcorehdr and replace it with the previous one on memory add/remove events. The memblock list is used to prepare the elfcorehdr. In the case of memory hot remove, the memblock list is updated after the arch crash hotplug handler is triggered, as depicted in Figure 1. Thus, the hot-removed memory is explicitly removed from the crash memory ranges to ensure that the memory ranges added to elfcorehdr do not include the hot-removed memory. Memory remove | v Offline pages | v Initiate memory notify call <----> crash hotplug handler chain for MEM_OFFLINE event | v Update memblock list Figure 1 There are two system calls, `kexec_file_load` and `kexec_load`, used to load the kdump image. A few changes have been made to ensure that the kernel can safely update the elfcorehdr component of the kdump image for both system calls. For the kexec_file_load syscall, kdump image is prepared in the kernel. To support an increasing number of memory regions, the elfcorehdr is built with extra buffer space to ensure that it can accommodate additional memory ranges in future. For the kexec_load syscall, the elfcorehdr is updated only if the KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag is passed to the kernel by the kexec tool. Passing this flag to the kernel indicates that the elfcorehdr is built to accommodate additional memory ranges and the elfcorehdr segment is not considered for SHA calculation, making it safe to update. The changes related to this feature are kept under the CRASH_HOTPLUG config, and it is enabled by default. Signed-off-by: Sourabh Jain Acked-by: Hari Bathini Signed-off-by: Michael Ellerman Link: https://msgid.link/20240326055413.186534-7-sourabhjain@linux.ibm.com

powerpc/crash: add crash CPU hotplug support

2024-04-23T05:00:04+00:00

Due to CPU/Memory hotplug or online/offline events, the elfcorehdr (which describes the CPUs and memory of the crashed kernel) and FDT (Flattened Device Tree) of kdump image becomes outdated. Consequently, attempting dump collection with an outdated elfcorehdr or FDT can lead to failed or inaccurate dump collection. Going forward, CPU hotplug or online/offline events are referred as CPU/Memory add/remove events. The current solution to address the above issue involves monitoring the CPU/Memory add/remove events in userspace using udev rules and whenever there are changes in CPU and memory resources, the entire kdump image is loaded again. The kdump image includes kernel, initrd, elfcorehdr, FDT, purgatory. Given that only elfcorehdr and FDT get outdated due to CPU/Memory add/remove events, reloading the entire kdump image is inefficient. More importantly, kdump remains inactive for a substantial amount of time until the kdump reload completes. To address the aforementioned issue, commit 247262756121 ("crash: add generic infrastructure for crash hotplug support") added a generic infrastructure that allows architectures to selectively update the kdump image component during CPU or memory add/remove events within the kernel itself. In the event of a CPU or memory add/remove events, the generic crash hotplug event handler, `crash_handle_hotplug_event()`, is triggered. It then acquires the necessary locks to update the kdump image and invokes the architecture-specific crash hotplug handler, `arch_crash_handle_hotplug_event()`, to update the required kdump image components. This patch adds crash hotplug handler for PowerPC and enable support to update the kdump image on CPU add/remove events. Support for memory add/remove events is added in a subsequent patch with the title "powerpc: add crash memory hotplug support" As mentioned earlier, only the elfcorehdr and FDT kdump image components need to be updated in the event of CPU or memory add/remove events. However, on PowerPC architecture crash hotplug handler only updates the FDT to enable crash hotplug support for CPU add/remove events. Here's why. The elfcorehdr on PowerPC is built with possible CPUs, and thus, it does not need an update on CPU add/remove events. On the other hand, the FDT needs to be updated on CPU add events to include the newly added CPU. If the FDT is not updated and the kernel crashes on a newly added CPU, the kdump kernel will fail to boot due to the unavailability of the crashing CPU in the FDT. During the early boot, it is expected that the boot CPU must be a part of the FDT; otherwise, the kernel will raise a BUG and fail to boot. For more information, refer to commit 36ae37e3436b0 ("powerpc: Make boot_cpuid common between 32 and 64-bit"). Since it is okay to have an offline CPU in the kdump FDT, no action is taken in case of CPU removal. There are two system calls, `kexec_file_load` and `kexec_load`, used to load the kdump image. Few changes have been made to ensure kernel can safely update the FDT of kdump image loaded using both system calls. For kexec_file_load syscall the kdump image is prepared in kernel. So to support an increasing number of CPUs, the FDT is constructed with extra buffer space to ensure it can accommodate a possible number of CPU nodes. Additionally, a call to fdt_pack (which trims the unused space once the FDT is prepared) is avoided if this feature is enabled. For the kexec_load syscall, the FDT is updated only if the KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag is passed to the kernel by userspace (kexec tools). When userspace passes this flag to the kernel, it indicates that the FDT is built to accommodate possible CPUs, and the FDT segment is excluded from SHA calculation, making it safe to update. The changes related to this feature are kept under the CRASH_HOTPLUG config, and it is enabled by default. Signed-off-by: Sourabh Jain Acked-by: Hari Bathini Signed-off-by: Michael Ellerman Link: https://msgid.link/20240326055413.186534-6-sourabhjain@linux.ibm.com

powerpc/kexec: make the update_cpus_node() function public

2024-04-23T04:59:51+00:00

Move the update_cpus_node() from kexec/{file_load_64.c => core_64.c} to allow other kexec components to use it. Later in the series, this function is used for in-kernel updates to the kdump image during CPU/memory hotplug or online/offline events for both kexec_load and kexec_file_load syscalls. No functional changes are intended. Signed-off-by: Sourabh Jain Acked-by: Hari Bathini Signed-off-by: Michael Ellerman Link: https://msgid.link/20240326055413.186534-5-sourabhjain@linux.ibm.com

kernel/linux.git/arch/powerpc/include/asm/kexec.h, branch linux-7.0.y

powerpc/crash: Update backup region offset in elfcorehdr on memory hotplug

powerpc/kdump: Add support for crashkernel CMA reservation

powerpc: Replace __ASSEMBLY__ with __ASSEMBLER__ in non-uapi headers

powerpc/crash: use generic crashkernel reservation

powerpc/crash: use generic APIs to locate memory hole for kdump

kexec: Consolidate machine_kexec_mask_interrupts() implementation

powerpc/kexec_file: fix extra size calculation for kexec FDT

powerpc/crash: add crash memory hotplug support

powerpc/crash: add crash CPU hotplug support

powerpc/kexec: make the update_cpus_node() function public

powerpc: Replace ASSEMBLY with ASSEMBLER in non-uapi headers