Merge our topic branch containing kdump hotplug changes, more detail from the original cover letter: 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. This patch series adds crash hotplug handler for PowerPC and enable support to update the kdump image on CPU/Memory add/remove events. Among the 6 patches in this series, the first two patches make changes to the generic crash hotplug handler to assist PowerPC in adding support for this feature. The last four patches add support for this feature. The following section outlines the problem addressed by this patch series, along with the current solution, its shortcomings, and the proposed resolution. Problem: ======== 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(which describes the CPUs and memory of the crashed kernel) and FDT (Flattened Device Tree) of kdump image becomes outdated. Consequently, attempting dump collection with an outdated elfcorehdr or FDT can lead to failed or inaccurate dump collection.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. Existing solution and its shortcoming: ====================================== 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 Given that only elfcorehdr and FDT get outdated due to CPU/Memory add/remove events, reloading the entire kdump image is inefficient.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. Proposed solution: ================== Instead of initiating a full kdump image reload from userspace on CPU/Memory hotplug and online/offline events, the proposed solution aims to update only the necessary kdump image component within the kernel itself.
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| @@ -13,6 +13,7 @@ · 12 unmodified lines | ||
| 13 | 13 | #define KEXEC_ON_CRASH 0x00000001 |
| 14 | 14 | #define KEXEC_PRESERVE_CONTEXT 0x00000002 |
| 15 | 15 | #define KEXEC_UPDATE_ELFCOREHDR 0x00000004 |
| 16 | +#define KEXEC_CRASH_HOTPLUG_SUPPORT 0x00000008 | |
| 16 | 17 | #define KEXEC_ARCH_MASK 0xffff0000 |
| 17 | 18 | |
| 18 | 19 | /* |