On 3/20/23 03:13, Baoquan He wrote:
On 03/17/23 at 05:21pm, Eric DeVolder wrote:
......
@@ -697,3 +700,137 @@ static int __init crash_save_vmcoreinfo_init(void)
}
subsys_initcall(crash_save_vmcoreinfo_init);
+
+#ifdef CONFIG_CRASH_HOTPLUG
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+/*
+ * To accurately reflect hot un/plug changes of cpu and memory resources
+ * (including onling and offlining of those resources), the elfcorehdr
+ * (which is passed to the crash kernel via the elfcorehdr= parameter)
+ * must be updated with the new list of CPUs and memories.
+ *
+ * In order to make changes to elfcorehdr, two conditions are needed:
+ * First, the segment containing the elfcorehdr must be large enough
+ * to permit a growing number of resources; the elfcorehdr memory size
+ * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
+ * Second, purgatory must explicitly exclude the elfcorehdr from the
+ * list of segments it checks (since the elfcorehdr changes and thus
+ * would require an update to purgatory itself to update the digest).
+ */
+static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
+{
+ /* Obtain lock while changing crash information */
+ if (!kexec_trylock())
+ return;
+
+ /* Check kdump is loaded */
+ if (kexec_crash_image) {
Here, what I mean is:
/* Obtain lock while changing crash information */
if (!kexec_trylock())
return;
/*If kdump is not loaded*/
if (!kexec_crash_image)
goto out;
Then we reduce one tab of indentation for the following code block, e.g
the for loop block will have smaller pressure on breaking the 80 chars
limitation.
Ah, yes, ok. I'll make that change. Do you prefer I post that soon, or give this v20 some more time?
eric
+ struct kimage *image = kexec_crash_image;
+
+ if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
+ hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
+ pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
+ else
+ pr_debug("hp_action %u\n", hp_action);
+
+ /*
+ * When the struct kimage is allocated, the elfcorehdr_index
+ * is set to -1. Find the segment containing the elfcorehdr,
+ * if not already found. This works for both the kexec_load
+ * and kexec_file_load paths.
+ */
+ if (image->elfcorehdr_index < 0) {
+ unsigned long mem;
+ unsigned char *ptr;
+ unsigned int n;
+
+ for (n = 0; n < image->nr_segments; n++) {
+ mem = image->segment[n].mem;
+ ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
+ if (ptr) {
+ /* The segment containing elfcorehdr */
+ if (memcmp(ptr, ELFMAG, SELFMAG) == 0)
+ image->elfcorehdr_index = (int)n;
+ kunmap_local(ptr);
+ }
+ }
+ }
+
+ if (image->elfcorehdr_index < 0) {
+ pr_err("unable to locate elfcorehdr segment");
+ goto out;
+ }
+
+ /* Needed in order for the segments to be updated */
+ arch_kexec_unprotect_crashkres();
+
+ /* Differentiate between normal load and hotplug update */
+ image->hp_action = hp_action;
+
+ /* Now invoke arch-specific update handler */
+ arch_crash_handle_hotplug_event(image);
+
+ /* No longer handling a hotplug event */
+ image->hp_action = KEXEC_CRASH_HP_NONE;
+ image->elfcorehdr_updated = true;
+
+ /* Change back to read-only */
+ arch_kexec_protect_crashkres();
+ }
+
+out:
+ /* Release lock now that update complete */
+ kexec_unlock();
+}
+
+static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
+{
+ switch (val) {
+ case MEM_ONLINE:
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+
+ case MEM_OFFLINE:
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block crash_memhp_nb = {
+ .notifier_call = crash_memhp_notifier,
+ .priority = 0
+};
+
+static int crash_cpuhp_online(unsigned int cpu)
+{
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
+ return 0;
+}
+
+static int crash_cpuhp_offline(unsigned int cpu)
+{
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
+ return 0;
+}
+
+static int __init crash_hotplug_init(void)
+{
+ int result = 0;
+
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ register_memory_notifier(&crash_memhp_nb);
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
+ "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
+ }
+
+ return result;
+}
+
+subsys_initcall(crash_hotplug_init);
+#endif
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 3d578c6fefee..8296d019737c 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -277,6 +277,12 @@ struct kimage *do_kimage_alloc_init(void)
/* Initialize the list of unusable pages */
INIT_LIST_HEAD(&image->unusable_pages);
+#ifdef CONFIG_CRASH_HOTPLUG
+ image->hp_action = KEXEC_CRASH_HP_NONE;
+ image->elfcorehdr_index = -1;
+ image->elfcorehdr_updated = false;
+#endif
+
return image;
}
--
2.31.1
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