[v12,6/6] powerpc: add crash memory hotplug support

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 53a4aa0b6b04..5e14279b83b8 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -113,6 +113,14 @@  int arch_crash_hotplug_cpu_support(struct kimage *image);
 #define arch_crash_hotplug_cpu_support arch_crash_hotplug_cpu_support
 #endif
 
+#ifdef CONFIG_MEMORY_HOTPLUG
+int arch_crash_hotplug_memory_support(struct kimage *image);
+#define arch_crash_hotplug_memory_support arch_crash_hotplug_memory_support
+#endif
+
+unsigned int arch_crash_get_elfcorehdr_size(void);
+#define crash_get_elfcorehdr_size arch_crash_get_elfcorehdr_size
+
 #endif /*CONFIG_CRASH_HOTPLUG */
 #endif /* CONFIG_PPC64 */
 
diff --git a/arch/powerpc/include/asm/kexec_ranges.h b/arch/powerpc/include/asm/kexec_ranges.h
index f83866a19e87..802abf580cf0 100644
--- a/arch/powerpc/include/asm/kexec_ranges.h
+++ b/arch/powerpc/include/asm/kexec_ranges.h
@@ -7,6 +7,7 @@ 
 void sort_memory_ranges(struct crash_mem *mrngs, bool merge);
 struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges);
 int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
+int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
 int add_tce_mem_ranges(struct crash_mem **mem_ranges);
 int add_initrd_mem_range(struct crash_mem **mem_ranges);
 #ifdef CONFIG_PPC_64S_HASH_MMU
diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c
index a8e845fb3eaa..2a38e52060dc 100644
--- a/arch/powerpc/kexec/core_64.c
+++ b/arch/powerpc/kexec/core_64.c
@@ -19,8 +19,10 @@ 
 #include <linux/of.h>
 #include <linux/libfdt.h>
 #include <linux/memblock.h>
+#include <linux/memory.h>
 
 #include <asm/page.h>
+#include <asm/drmem.h>
 #include <asm/current.h>
 #include <asm/machdep.h>
 #include <asm/cacheflush.h>
@@ -547,9 +549,7 @@  int update_cpus_node(void *fdt)
 #undef pr_fmt
 #define pr_fmt(fmt) "crash hp: " fmt
 
-#ifdef CONFIG_HOTPLUG_CPU
- /* Provides the value for the sysfs crash_hotplug nodes */
-int arch_crash_hotplug_cpu_support(struct kimage *image)
+static int crash_hotplug_support(struct kimage *image)
 {
 	if (image->file_mode)
 		return 1;
@@ -560,8 +560,118 @@  int arch_crash_hotplug_cpu_support(struct kimage *image)
 	 */
 	return image->update_elfcorehdr && image->update_fdt;
 }
+
+#ifdef CONFIG_HOTPLUG_CPU
+ /* Provides the value for the sysfs crash_hotplug nodes */
+int arch_crash_hotplug_cpu_support(struct kimage *image)
+{
+	return crash_hotplug_support(image);
+}
+#endif
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+ /* Provides the value for the sysfs memory_hotplug nodes */
+int arch_crash_hotplug_memory_support(struct kimage *image)
+{
+	return crash_hotplug_support(image);
+}
 #endif
 
+/*
+ * Advertise preferred elfcorehdr size to userspace via
+ * /sys/kernel/crash_elfcorehdr_size sysfs interface.
+ */
+unsigned int arch_crash_get_elfcorehdr_size(void)
+{
+	unsigned int sz;
+	unsigned long elf_phdr_cnt;
+
+	/* Program header for CPU notes and vmcoreinfo */
+	elf_phdr_cnt = 2;
+	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+		/* In the worst case, a Phdr is needed for every other LMB to be
+		 * represented as an individual crash range.
+		 */
+		elf_phdr_cnt += memory_hotplug_max() / (2 * drmem_lmb_size());
+
+	/* Do not cross the max limit */
+	if (elf_phdr_cnt > PN_XNUM)
+		elf_phdr_cnt = PN_XNUM;
+
+	sz = sizeof(struct elfhdr) + (elf_phdr_cnt * sizeof(Elf64_Phdr));
+	return sz;
+}
+
+/**
+ * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with old
+ *			       elfcorehdr in the kexec segment array.
+ * @image: the active struct kimage
+ * @mn: struct memory_notify data handler
+ */
+static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *mn)
+{
+	int ret;
+	struct crash_mem *cmem = NULL;
+	struct kexec_segment *ksegment;
+	void *ptr, *mem, *elfbuf = NULL;
+	unsigned long elfsz, memsz, base_addr, size;
+
+	ksegment = &image->segment[image->elfcorehdr_index];
+	mem = (void *) ksegment->mem;
+	memsz = ksegment->memsz;
+
+	ret = get_crash_memory_ranges(&cmem);
+	if (ret) {
+		pr_err("Failed to get crash mem range\n");
+		return;
+	}
+
+	/*
+	 * The hot unplugged memory is part of crash memory ranges,
+	 * remove it here.
+	 */
+	if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
+		base_addr = PFN_PHYS(mn->start_pfn);
+		size = mn->nr_pages * PAGE_SIZE;
+		ret = remove_mem_range(&cmem, base_addr, size);
+		if (ret) {
+			pr_err("Failed to remove hot-unplugged from crash memory ranges.\n");
+			return;
+		}
+	}
+
+	ret = crash_prepare_elf64_headers(cmem, false, &elfbuf, &elfsz);
+	if (ret) {
+		pr_err("Failed to prepare elf header\n");
+		return;
+	}
+
+	/*
+	 * It is unlikely that kernel hit this because elfcorehdr kexec
+	 * segment (memsz) is built with addition space to accommodate growing
+	 * number of crash memory ranges while loading the kdump kernel. It is
+	 * Just to avoid any unforeseen case.
+	 */
+	if (elfsz > memsz) {
+		pr_err("Updated crash elfcorehdr elfsz %lu > memsz %lu", elfsz, memsz);
+		goto out;
+	}
+
+	ptr = __va(mem);
+	if (ptr) {
+		/* Temporarily invalidate the crash image while it is replaced */
+		xchg(&kexec_crash_image, NULL);
+
+		/* Replace the old elfcorehdr with newly prepared elfcorehdr */
+		memcpy((void *)ptr, elfbuf, elfsz);
+
+		/* The crash image is now valid once again */
+		xchg(&kexec_crash_image, image);
+	}
+out:
+	vfree(elfbuf);
+}
+
 /**
  * arch_crash_handle_hotplug_event - Handle crash CPU/Memory hotplug events to update the
  *				     necessary kexec segments based on the hotplug event.
@@ -572,7 +682,7 @@  int arch_crash_hotplug_cpu_support(struct kimage *image)
  * CPU addition: Update the FDT segment to include the newly added CPU.
  * CPU removal: No action is needed, with the assumption that it's okay to have offline CPUs
  *		as part of the FDT.
- * Memory addition/removal: No action is taken as this is not yet supported.
+ * Memory addition/removal: Recreate the elfcorehdr segment
  */
 void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 {
@@ -593,7 +703,6 @@  void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 		return;
 
 	} else if (hp_action == KEXEC_CRASH_HP_ADD_CPU) {
-
 		void *fdt, *ptr;
 		unsigned long mem;
 		int i, fdt_index = -1;
@@ -628,8 +737,10 @@  void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 
 	} else if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY ||
 		   hp_action == KEXEC_CRASH_HP_ADD_MEMORY) {
-		pr_info_once("Crash update is not supported for memory hotplug\n");
-		return;
+		struct memory_notify *mn;
+
+		mn = (struct memory_notify *)arg;
+		update_crash_elfcorehdr(image, mn);
 	}
 }
 #endif
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index c8eec15b38ff..4907d00bf265 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -21,6 +21,8 @@ 
 #include <linux/memblock.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/elf.h>
+
 #include <asm/setup.h>
 #include <asm/drmem.h>
 #include <asm/firmware.h>
@@ -739,7 +741,35 @@  static int load_elfcorehdr_segment(struct kimage *image, struct kexec_buf *kbuf)
 
 	kbuf->buffer = headers;
 	kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
-	kbuf->bufsz = kbuf->memsz = headers_sz;
+	kbuf->bufsz = headers_sz;
+#if defined(CONFIG_CRASH_HOTPLUG) && defined(CONFIG_MEMORY_HOTPLUG)
+	/* Adjust the elfcorehdr segment size to accommodate
+	 * future crash memory ranges.
+	 */
+	int max_lmb;
+	unsigned long pnum;
+
+	/* In the worst case, a Phdr is needed for every other LMB to be
+	 * represented as an individual crash range.
+	 */
+	max_lmb = memory_hotplug_max() / (2 * drmem_lmb_size());
+
+	/* Do not cross the Phdr max limit of the elf header.
+	 * Avoid counting Phdr for crash ranges (cmem->nr_ranges)
+	 * which are already part of elfcorehdr.
+	 */
+	if (max_lmb > PN_XNUM)
+		pnum = PN_XNUM - cmem->nr_ranges;
+	else
+		pnum = max_lmb - cmem->nr_ranges;
+
+	/* Additional buffer space for elfcorehdr to accommodate
+	 * future memory ranges.
+	 */
+	kbuf->memsz = headers_sz + pnum * sizeof(Elf64_Phdr);
+#else
+	kbuf->memsz = headers_sz;
+#endif
 	kbuf->top_down = false;
 
 	ret = kexec_add_buffer(kbuf);
@@ -749,7 +779,7 @@  static int load_elfcorehdr_segment(struct kimage *image, struct kexec_buf *kbuf)
 	}
 
 	image->elf_load_addr = kbuf->mem;
-	image->elf_headers_sz = headers_sz;
+	image->elf_headers_sz = kbuf->memsz;
 	image->elf_headers = headers;
 out:
 	kfree(cmem);
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index fb3e12f15214..4fd0c5d5607b 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -234,6 +234,91 @@  int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size)
 	return __add_mem_range(mem_ranges, base, size);
 }
 
+/**
+ * remove_mem_range - Removes the given memory range from the range list.
+ * @mem_ranges:    Range list to remove the memory range to.
+ * @base:          Base address of the range to remove.
+ * @size:          Size of the memory range to remove.
+ *
+ * (Re)allocates memory, if needed.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size)
+{
+	u64 end;
+	int ret = 0;
+	unsigned int i;
+	u64 mstart, mend;
+	struct crash_mem *mem_rngs = *mem_ranges;
+
+	if (!size)
+		return 0;
+
+	/*
+	 * Memory range are stored as start and end address, use
+	 * the same format to do remove operation.
+	 */
+	end = base + size - 1;
+
+	for (i = 0; i < mem_rngs->nr_ranges; i++) {
+		mstart = mem_rngs->ranges[i].start;
+		mend = mem_rngs->ranges[i].end;
+
+		/*
+		 * Memory range to remove is not part of this range entry
+		 * in the memory range list
+		 */
+		if (!(base >= mstart && end <= mend))
+			continue;
+
+		/*
+		 * Memory range to remove is equivalent to this entry in the
+		 * memory range list. Remove the range entry from the list.
+		 */
+		if (base == mstart && end == mend) {
+			for (; i < mem_rngs->nr_ranges - 1; i++) {
+				mem_rngs->ranges[i].start = mem_rngs->ranges[i+1].start;
+				mem_rngs->ranges[i].end = mem_rngs->ranges[i+1].end;
+			}
+			mem_rngs->nr_ranges--;
+			goto out;
+		}
+		/*
+		 * Start address of the memory range to remove and the
+		 * current memory range entry in the list is same. Just
+		 * move the start address of the current memory range
+		 * entry in the list to end + 1.
+		 */
+		else if (base == mstart) {
+			mem_rngs->ranges[i].start = end + 1;
+			goto out;
+		}
+		/*
+		 * End address of the memory range to remove and the
+		 * current memory range entry in the list is same.
+		 * Just move the end address of the current memory
+		 * range entry in the list to base - 1.
+		 */
+		else if (end == mend)  {
+			mem_rngs->ranges[i].end = base - 1;
+			goto out;
+		}
+		/*
+		 * Memory range to remove is not at the edge of current
+		 * memory range entry. Split the current memory entry into
+		 * two half.
+		 */
+		else {
+			mem_rngs->ranges[i].end = base - 1;
+			size = mem_rngs->ranges[i].end - end;
+			ret = add_mem_range(mem_ranges, end + 1, size);
+		}
+	}
+out:
+	return ret;
+}
+
 /**
  * add_tce_mem_ranges - Adds tce-table range to the given memory ranges list.
  * @mem_ranges:         Range list to add the memory range(s) to.