[PATCH v6 0/5] arm64/riscv: Add support for crashkernel CMA reservation

[PATCH v6 0/5] arm64/riscv: Add support for crashkernel CMA reservation

[Jinjie Ruan]

The crash memory allocation, and the exclude of crashk_res, crashk_low_res
and crashk_cma memory are almost identical across different architectures,
This patch set handle them in crash core in a general way, which eliminate
a lot of duplication code.

And add support for crashkernel CMA reservation for arm64 and riscv.

Rebased on v7.0-rc1.

Basic test were performed on QEMU platforms for x86, ARM64, and RISC-V
architectures with the following parameters:

	"cma=256M crashkernel=256M crashkernel=64M,cma"

Changes in v6:
- Update the crash core exclude code as Mike suggested.
- Rebased on v7.0-rc1.
- Add acked-by.
- Link to v5: https://lore.kernel.org/all/20260212101001.343158-1-ruanjinjie@huawei.com/

Changes in v5:
- Fix the kernel test robot build warnings.
- Sort crash memory ranges before preparing elfcorehdr for powerpc
- Link to v4: https://lore.kernel.org/all/20260209095931.2813152-1-ruanjinjie@huawei.com/

Changes in v4:
- Move the size calculation (and the realloc if needed) into the
  generic crash.
- Link to v3: https://lore.kernel.org/all/20260204093728.1447527-1-ruanjinjie@huawei.com/

Changs in v3:
- Exclude crash kernel memory in crash core as Mike suggested.
- Add acked-by.

Jinjie Ruan (4):
  crash: Exclude crash kernel memory in crash core
  crash: Use crash_exclude_core_ranges() on powerpc
  arm64: kexec: Add support for crashkernel CMA reservation
  riscv: kexec: Add support for crashkernel CMA reservation

Sourabh Jain (1):
  powerpc/crash: sort crash memory ranges before preparing elfcorehdr

 .../admin-guide/kernel-parameters.txt         |  16 +--
 arch/arm64/kernel/machine_kexec_file.c        |  41 +++----
 arch/arm64/mm/init.c                          |   5 +-
 arch/loongarch/kernel/machine_kexec_file.c    |  39 +++----
 arch/powerpc/include/asm/kexec_ranges.h       |   4 +-
 arch/powerpc/kexec/crash.c                    |   5 +-
 arch/powerpc/kexec/ranges.c                   | 101 +-----------------
 arch/riscv/kernel/machine_kexec_file.c        |  40 ++++---
 arch/riscv/mm/init.c                          |   5 +-
 arch/x86/kernel/crash.c                       |  89 +++------------
 include/linux/crash_core.h                    |   9 ++
 kernel/crash_core.c                           |  89 ++++++++++++++-
 12 files changed, 178 insertions(+), 265 deletions(-)

-- 
2.34.1

[PATCH v6 1/5] powerpc/crash: sort crash memory ranges before preparing elfcorehdr

[Jinjie Ruan]

From: Sourabh Jain <sourabhjain@linux.ibm.com>

During a memory hot-remove event, the elfcorehdr is rebuilt to exclude
the removed memory. While updating the crash memory ranges for this
operation, the crash memory ranges array can become unsorted. This
happens because remove_mem_range() may split a memory range into two
parts and append the higher-address part as a separate range at the end
of the array.

So far, no issues have been observed due to the unsorted crash memory
ranges. However, this could lead to problems once crash memory range
removal is handled by generic code, as introduced in the upcoming
patches in this series.

Currently, powerpc uses a platform-specific function,
remove_mem_range(), to exclude hot-removed memory from the crash memory
ranges. This function performs the same task as the generic
crash_exclude_mem_range() in crash_core.c. The generic helper also
ensures that the crash memory ranges remain sorted. So remove the
redundant powerpc-specific implementation and instead call
crash_exclude_mem_range_guarded() (which internally calls
crash_exclude_mem_range()) to exclude the hot-removed memory ranges.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan he <bhe@redhat.com>
Cc: Jinjie Ruan <ruanjinjie@huawei.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 arch/powerpc/include/asm/kexec_ranges.h |  4 +-
 arch/powerpc/kexec/crash.c              |  5 +-
 arch/powerpc/kexec/ranges.c             | 87 +------------------------
 3 files changed, 7 insertions(+), 89 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec_ranges.h b/arch/powerpc/include/asm/kexec_ranges.h
index 14055896cbcb..ad95e3792d10 100644
--- a/arch/powerpc/include/asm/kexec_ranges.h
+++ b/arch/powerpc/include/asm/kexec_ranges.h
@@ -7,7 +7,9 @@
 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 crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
+				    unsigned long long mstart,
+				    unsigned long long mend);
 int get_exclude_memory_ranges(struct crash_mem **mem_ranges);
 int get_reserved_memory_ranges(struct crash_mem **mem_ranges);
 int get_crash_memory_ranges(struct crash_mem **mem_ranges);
diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index a325c1c02f96..898742a5205c 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -431,7 +431,7 @@ static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *
 	struct crash_mem *cmem = NULL;
 	struct kexec_segment *ksegment;
 	void *ptr, *mem, *elfbuf = NULL;
-	unsigned long elfsz, memsz, base_addr, size;
+	unsigned long elfsz, memsz, base_addr, size, end;
 
 	ksegment = &image->segment[image->elfcorehdr_index];
 	mem = (void *) ksegment->mem;
@@ -450,7 +450,8 @@ static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *
 	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);
+		end = base_addr + size - 1;
+		ret = crash_exclude_mem_range_guarded(&cmem, base_addr, end);
 		if (ret) {
 			pr_err("Failed to remove hot-unplugged memory from crash memory ranges\n");
 			goto out;
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index 867135560e5c..6c58bcc3e130 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -553,7 +553,7 @@ int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 #endif /* CONFIG_KEXEC_FILE */
 
 #ifdef CONFIG_CRASH_DUMP
-static int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
+int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
 					   unsigned long long mstart,
 					   unsigned long long mend)
 {
@@ -641,89 +641,4 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
 		pr_err("Failed to setup crash memory ranges\n");
 	return ret;
 }
-
-/**
- * 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 {
-			size = mem_rngs->ranges[i].end - end + 1;
-			mem_rngs->ranges[i].end = base - 1;
-			ret = add_mem_range(mem_ranges, end + 1, size);
-		}
-	}
-out:
-	return ret;
-}
 #endif /* CONFIG_CRASH_DUMP */
-- 
2.34.1

[PATCH v6 2/5] crash: Exclude crash kernel memory in crash core

[Jinjie Ruan]

The crash memory alloc, and the exclude of crashk_res, crashk_low_res
and crashk_cma memory are almost identical across different architectures,
handling them in the crash core would eliminate a lot of duplication, so
do them in the common code.

To achieve the above goal, three architecture-specific functions are
introduced:

- arch_get_system_nr_ranges(). Pre-counts the max number of memory ranges.

- arch_crash_populate_cmem(). Collects the memory ranges and fills them
  into cmem.

- arch_crash_exclude_ranges(). Architecture's additional crash memory
  ranges exclusion, defaulting to empty.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/machine_kexec_file.c     | 39 +++-------
 arch/loongarch/kernel/machine_kexec_file.c | 39 +++-------
 arch/riscv/kernel/machine_kexec_file.c     | 38 +++------
 arch/x86/kernel/crash.c                    | 89 +++-------------------
 include/linux/crash_core.h                 |  5 ++
 kernel/crash_core.c                        | 82 +++++++++++++++++++-
 6 files changed, 132 insertions(+), 160 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index fba260ad87a9..c338506a580b 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -40,23 +40,23 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 }
 
 #ifdef CONFIG_CRASH_DUMP
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+unsigned int arch_get_system_nr_ranges(void)
 {
-	struct crash_mem *cmem;
-	unsigned int nr_ranges;
-	int ret;
-	u64 i;
+	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
 	phys_addr_t start, end;
+	u64 i;
 
-	nr_ranges = 2; /* for exclusion of crashkernel region */
 	for_each_mem_range(i, &start, &end)
 		nr_ranges++;
 
-	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
-	if (!cmem)
-		return -ENOMEM;
+	return nr_ranges;
+}
+
+int arch_crash_populate_cmem(struct crash_mem *cmem)
+{
+	phys_addr_t start, end;
+	u64 i;
 
-	cmem->max_nr_ranges = nr_ranges;
 	cmem->nr_ranges = 0;
 	for_each_mem_range(i, &start, &end) {
 		cmem->ranges[cmem->nr_ranges].start = start;
@@ -64,22 +64,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 		cmem->nr_ranges++;
 	}
 
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret)
-		goto out;
-
-	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
-		if (ret)
-			goto out;
-	}
-
-	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
-
-out:
-	kfree(cmem);
-	return ret;
+	return 0;
 }
 #endif
 
@@ -109,7 +94,7 @@ int load_other_segments(struct kimage *image,
 	void *headers;
 	unsigned long headers_sz;
 	if (image->type == KEXEC_TYPE_CRASH) {
-		ret = prepare_elf_headers(&headers, &headers_sz);
+		ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
 		if (ret) {
 			pr_err("Preparing elf core header failed\n");
 			goto out_err;
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 5584b798ba46..4b318a94b564 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -56,23 +56,23 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
 }
 
 #ifdef CONFIG_CRASH_DUMP
-
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+unsigned int arch_get_system_nr_ranges(void)
 {
-	int ret, nr_ranges;
-	uint64_t i;
+	int nr_ranges = 2; /* for exclusion of crashkernel region */
 	phys_addr_t start, end;
-	struct crash_mem *cmem;
+	uint64_t i;
 
-	nr_ranges = 2; /* for exclusion of crashkernel region */
 	for_each_mem_range(i, &start, &end)
 		nr_ranges++;
 
-	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
-	if (!cmem)
-		return -ENOMEM;
+	return nr_ranges;
+}
+
+int arch_crash_populate_cmem(struct crash_mem *cmem)
+{
+	phys_addr_t start, end;
+	uint64_t i;
 
-	cmem->max_nr_ranges = nr_ranges;
 	cmem->nr_ranges = 0;
 	for_each_mem_range(i, &start, &end) {
 		cmem->ranges[cmem->nr_ranges].start = start;
@@ -80,22 +80,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 		cmem->nr_ranges++;
 	}
 
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret < 0)
-		goto out;
-
-	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
-		if (ret < 0)
-			goto out;
-	}
-
-	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
-
-out:
-	kfree(cmem);
-	return ret;
+	return 0;
 }
 
 /*
@@ -163,7 +148,7 @@ int load_other_segments(struct kimage *image,
 		void *headers;
 		unsigned long headers_sz;
 
-		ret = prepare_elf_headers(&headers, &headers_sz);
+		ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
 		if (ret < 0) {
 			pr_err("Preparing elf core header failed\n");
 			goto out_err;
diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index 54e2d9552e93..d0e331d87155 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -44,6 +44,15 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 	return 0;
 }
 
+unsigned int arch_get_system_nr_ranges(void)
+{
+	unsigned int nr_ranges = 1; /* For exclusion of crashkernel region */
+
+	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
+
+	return nr_ranges;
+}
+
 static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 {
 	struct crash_mem *cmem = arg;
@@ -55,33 +64,10 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 	return 0;
 }
 
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+int arch_crash_populate_cmem(struct crash_mem *cmem)
 {
-	struct crash_mem *cmem;
-	unsigned int nr_ranges;
-	int ret;
-
-	nr_ranges = 1; /* For exclusion of crashkernel region */
-	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
-
-	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
-	if (!cmem)
-		return -ENOMEM;
-
-	cmem->max_nr_ranges = nr_ranges;
 	cmem->nr_ranges = 0;
-	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
-	if (ret)
-		goto out;
-
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (!ret)
-		ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
-
-out:
-	kfree(cmem);
-	return ret;
+	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
 }
 
 static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
@@ -273,7 +259,7 @@ int load_extra_segments(struct kimage *image, unsigned long kernel_start,
 	if (image->type == KEXEC_TYPE_CRASH) {
 		void *headers;
 		unsigned long headers_sz;
-		ret = prepare_elf_headers(&headers, &headers_sz);
+		ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
 		if (ret) {
 			pr_err("Preparing elf core header failed\n");
 			goto out;
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 335fd2ee9766..3ad3f8b758a4 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -152,16 +152,8 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 	return 0;
 }
 
-/* Gather all the required information to prepare elf headers for ram regions */
-static struct crash_mem *fill_up_crash_elf_data(void)
+unsigned int arch_get_system_nr_ranges(void)
 {
-	unsigned int nr_ranges = 0;
-	struct crash_mem *cmem;
-
-	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
-	if (!nr_ranges)
-		return NULL;
-
 	/*
 	 * Exclusion of crash region, crashk_low_res and/or crashk_cma_ranges
 	 * may cause range splits. So add extra slots here.
@@ -176,49 +168,16 @@ static struct crash_mem *fill_up_crash_elf_data(void)
 	 * But in order to lest the low 1M could be changed in the future,
 	 * (e.g. [start, 1M]), add a extra slot.
 	 */
-	nr_ranges += 3 + crashk_cma_cnt;
-	cmem = vzalloc(struct_size(cmem, ranges, nr_ranges));
-	if (!cmem)
-		return NULL;
-
-	cmem->max_nr_ranges = nr_ranges;
+	unsigned int nr_ranges = 3 + crashk_cma_cnt;
 
-	return cmem;
+	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
+	return nr_ranges;
 }
 
-/*
- * Look for any unwanted ranges between mstart, mend and remove them. This
- * might lead to split and split ranges are put in cmem->ranges[] array
- */
-static int elf_header_exclude_ranges(struct crash_mem *cmem)
+int arch_crash_exclude_ranges(struct crash_mem *cmem)
 {
-	int ret = 0;
-	int i;
-
 	/* Exclude the low 1M because it is always reserved */
-	ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
-	if (ret)
-		return ret;
-
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret)
-		return ret;
-
-	if (crashk_low_res.end)
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start,
-					      crashk_low_res.end);
-	if (ret)
-		return ret;
-
-	for (i = 0; i < crashk_cma_cnt; ++i) {
-		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
-					      crashk_cma_ranges[i].end);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
+	return crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
 }
 
 static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
@@ -232,35 +191,9 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 	return 0;
 }
 
-/* Prepare elf headers. Return addr and size */
-static int prepare_elf_headers(void **addr, unsigned long *sz,
-			       unsigned long *nr_mem_ranges)
+int arch_crash_populate_cmem(struct crash_mem *cmem)
 {
-	struct crash_mem *cmem;
-	int ret;
-
-	cmem = fill_up_crash_elf_data();
-	if (!cmem)
-		return -ENOMEM;
-
-	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
-	if (ret)
-		goto out;
-
-	/* Exclude unwanted mem ranges */
-	ret = elf_header_exclude_ranges(cmem);
-	if (ret)
-		goto out;
-
-	/* Return the computed number of memory ranges, for hotplug usage */
-	*nr_mem_ranges = cmem->nr_ranges;
-
-	/* By default prepare 64bit headers */
-	ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
-
-out:
-	vfree(cmem);
-	return ret;
+	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
 }
 #endif
 
@@ -418,7 +351,8 @@ int crash_load_segments(struct kimage *image)
 				  .buf_max = ULONG_MAX, .top_down = false };
 
 	/* Prepare elf headers and add a segment */
-	ret = prepare_elf_headers(&kbuf.buffer, &kbuf.bufsz, &pnum);
+	ret = crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &kbuf.buffer,
+				    &kbuf.bufsz, &pnum);
 	if (ret)
 		return ret;
 
@@ -529,7 +463,8 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 	 * Create the new elfcorehdr reflecting the changes to CPU and/or
 	 * memory resources.
 	 */
-	if (prepare_elf_headers(&elfbuf, &elfsz, &nr_mem_ranges)) {
+	if (crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz,
+				  &nr_mem_ranges)) {
 		pr_err("unable to create new elfcorehdr");
 		goto out;
 	}
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index d35726d6a415..033b20204aca 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -66,6 +66,8 @@ extern int crash_exclude_mem_range(struct crash_mem *mem,
 				   unsigned long long mend);
 extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 				       void **addr, unsigned long *sz);
+extern int crash_prepare_headers(int need_kernel_map, void **addr,
+				 unsigned long *sz, unsigned long *nr_mem_ranges);
 
 struct kimage;
 struct kexec_segment;
@@ -83,6 +85,9 @@ int kexec_should_crash(struct task_struct *p);
 int kexec_crash_loaded(void);
 void crash_save_cpu(struct pt_regs *regs, int cpu);
 extern int kimage_crash_copy_vmcoreinfo(struct kimage *image);
+extern unsigned int arch_get_system_nr_ranges(void);
+extern int arch_crash_populate_cmem(struct crash_mem *cmem);
+extern int arch_crash_exclude_ranges(struct crash_mem *cmem);
 
 #else /* !CONFIG_CRASH_DUMP*/
 struct pt_regs;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 2c1a3791e410..96a96e511f5a 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -170,9 +170,6 @@ static inline resource_size_t crash_resource_size(const struct resource *res)
 	return !res->end ? 0 : resource_size(res);
 }
 
-
-
-
 int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 			  void **addr, unsigned long *sz)
 {
@@ -274,6 +271,85 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 	return 0;
 }
 
+static struct crash_mem *alloc_cmem(unsigned int nr_ranges)
+{
+	struct crash_mem *cmem;
+
+	cmem = kvzalloc_flex(*cmem, ranges, nr_ranges);
+	if (!cmem)
+		return NULL;
+
+	cmem->max_nr_ranges = nr_ranges;
+	return cmem;
+}
+
+unsigned int __weak arch_get_system_nr_ranges(void) { return 0; }
+int __weak arch_crash_populate_cmem(struct crash_mem *cmem) { return -1; }
+int __weak arch_crash_exclude_ranges(struct crash_mem *cmem) { return 0; }
+
+static int crash_exclude_core_ranges(struct crash_mem *cmem)
+{
+	int ret, i;
+
+	/* Exclude crashkernel region */
+	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+	if (ret)
+		return ret;
+
+	if (crashk_low_res.end) {
+		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+		if (ret)
+			return ret;
+	}
+
+	for (i = 0; i < crashk_cma_cnt; ++i) {
+		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
+					      crashk_cma_ranges[i].end);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz,
+			  unsigned long *nr_mem_ranges)
+{
+	unsigned int max_nr_ranges;
+	struct crash_mem *cmem;
+	int ret;
+
+	max_nr_ranges = arch_get_system_nr_ranges();
+	if (!max_nr_ranges)
+		return -ENOMEM;
+
+	cmem = alloc_cmem(max_nr_ranges);
+	if (!cmem)
+		return -ENOMEM;
+
+	ret = arch_crash_populate_cmem(cmem);
+	if (ret)
+		goto out;
+
+	ret = crash_exclude_core_ranges(cmem);
+	if (ret)
+		goto out;
+
+	ret = arch_crash_exclude_ranges(cmem);
+	if (ret)
+		goto out;
+
+	/* Return the computed number of memory ranges, for hotplug usage */
+	if (nr_mem_ranges)
+		*nr_mem_ranges = cmem->nr_ranges;
+
+	ret = crash_prepare_elf64_headers(cmem, need_kernel_map, addr, sz);
+
+out:
+	kvfree(cmem);
+	return ret;
+}
+
 /**
  * crash_exclude_mem_range - exclude a mem range for existing ranges
  * @mem: mem->range contains an array of ranges sorted in ascending order
-- 
2.34.1

[PATCH v6 3/5] crash: Use crash_exclude_core_ranges() on powerpc

[Jinjie Ruan]

The crash memory exclude of crashk_res and crashk_cma memory on powerpc
are almost identical to the generic crash_exclude_core_ranges().

By introducing the architecture-specific arch_crash_exclude_mem_range()
function with a default implementation of crash_exclude_mem_range(),
and using crash_exclude_mem_range_guarded as powerpc's separate
implementation, the generic crash_exclude_core_ranges() helper function
can be reused.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/powerpc/kexec/ranges.c | 16 ++++------------
 include/linux/crash_core.h  |  4 ++++
 kernel/crash_core.c         | 19 +++++++++++++------
 3 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index 6c58bcc3e130..e5fea23b191b 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -553,9 +553,9 @@ int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 #endif /* CONFIG_KEXEC_FILE */
 
 #ifdef CONFIG_CRASH_DUMP
-int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
-					   unsigned long long mstart,
-					   unsigned long long mend)
+int arch_crash_exclude_mem_range(struct crash_mem **mem_ranges,
+				 unsigned long long mstart,
+				 unsigned long long mend)
 {
 	struct crash_mem *tmem = *mem_ranges;
 
@@ -604,18 +604,10 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
 			sort_memory_ranges(*mem_ranges, true);
 	}
 
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range_guarded(mem_ranges, crashk_res.start, crashk_res.end);
+	ret = crash_exclude_core_ranges(mem_ranges);
 	if (ret)
 		goto out;
 
-	for (i = 0; i < crashk_cma_cnt; ++i) {
-		ret = crash_exclude_mem_range_guarded(mem_ranges, crashk_cma_ranges[i].start,
-					      crashk_cma_ranges[i].end);
-		if (ret)
-			goto out;
-	}
-
 	/*
 	 * FIXME: For now, stay in parity with kexec-tools but if RTAS/OPAL
 	 *        regions are exported to save their context at the time of
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 033b20204aca..dbec826dc53b 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -68,6 +68,7 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_ma
 				       void **addr, unsigned long *sz);
 extern int crash_prepare_headers(int need_kernel_map, void **addr,
 				 unsigned long *sz, unsigned long *nr_mem_ranges);
+extern int crash_exclude_core_ranges(struct crash_mem **cmem);
 
 struct kimage;
 struct kexec_segment;
@@ -88,6 +89,9 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage *image);
 extern unsigned int arch_get_system_nr_ranges(void);
 extern int arch_crash_populate_cmem(struct crash_mem *cmem);
 extern int arch_crash_exclude_ranges(struct crash_mem *cmem);
+extern int arch_crash_exclude_mem_range(struct crash_mem **mem,
+					unsigned long long mstart,
+					unsigned long long mend);
 
 #else /* !CONFIG_CRASH_DUMP*/
 struct pt_regs;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 96a96e511f5a..300d44ad5471 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -287,24 +287,31 @@ unsigned int __weak arch_get_system_nr_ranges(void) { return 0; }
 int __weak arch_crash_populate_cmem(struct crash_mem *cmem) { return -1; }
 int __weak arch_crash_exclude_ranges(struct crash_mem *cmem) { return 0; }
 
-static int crash_exclude_core_ranges(struct crash_mem *cmem)
+int __weak arch_crash_exclude_mem_range(struct crash_mem **mem,
+					unsigned long long mstart,
+					unsigned long long mend)
+{
+	return crash_exclude_mem_range(*mem, mstart, mend);
+}
+
+int crash_exclude_core_ranges(struct crash_mem **cmem)
 {
 	int ret, i;
 
 	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+	ret = arch_crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
 	if (ret)
 		return ret;
 
 	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+		ret = arch_crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
 		if (ret)
 			return ret;
 	}
 
 	for (i = 0; i < crashk_cma_cnt; ++i) {
-		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
-					      crashk_cma_ranges[i].end);
+		ret = arch_crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
+						   crashk_cma_ranges[i].end);
 		if (ret)
 			return ret;
 	}
@@ -331,7 +338,7 @@ int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz,
 	if (ret)
 		goto out;
 
-	ret = crash_exclude_core_ranges(cmem);
+	ret = crash_exclude_core_ranges(&cmem);
 	if (ret)
 		goto out;
 
-- 
2.34.1

[PATCH v6 4/5] arm64: kexec: Add support for crashkernel CMA reservation

[Jinjie Ruan]

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.

Crash kernel memory reservation wastes production resources if too
large, risks kdump failure if too small, and faces allocation difficulties
on fragmented systems due to contiguous block constraints. The new
CMA-based crashkernel reservation scheme splits the "large fixed
reservation" into a "small fixed region + large CMA dynamic region": the
CMA memory is available to userspace during normal operation to avoid
waste, and is reclaimed for kdump upon crash—saving memory while
improving reliability.

So extend crashkernel CMA reservation support to arm64. The following
changes are made to enable CMA reservation:

- 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 for kdump kernel to use.
- Exclude the CMA-reserved ranges from the crash kernel memory to
  prevent them from being exported through /proc/vmcore, which is already
  done in the crash core.

Update kernel-parameters.txt to document CMA support for crashkernel on
arm64 architecture.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
v3:
- Add Acked-by.
v2:
- Free cmem in prepare_elf_headers()
- Add the mtivation.
---
 Documentation/admin-guide/kernel-parameters.txt | 2 +-
 arch/arm64/kernel/machine_kexec_file.c          | 8 +++++++-
 arch/arm64/mm/init.c                            | 5 +++--
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index cb850e5290c2..497f63b76898 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1121,7 +1121,7 @@ Kernel parameters
 			It will be ignored when crashkernel=X,high is not used
 			or memory reserved is below 4G.
 	crashkernel=size[KMG],cma
-			[KNL, X86, ppc] Reserve additional crash kernel memory from
+			[KNL, X86, ARM64, ppc] Reserve additional crash kernel memory from
 			CMA. This reservation is usable by the first system's
 			userspace memory and kernel movable allocations (memory
 			balloon, zswap). Pages allocated from this memory range
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index c338506a580b..c8862a762eb3 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -42,7 +42,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 #ifdef CONFIG_CRASH_DUMP
 unsigned int arch_get_system_nr_ranges(void)
 {
-	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
+	unsigned int nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */
 	phys_addr_t start, end;
 	u64 i;
 
@@ -64,6 +64,12 @@ int arch_crash_populate_cmem(struct crash_mem *cmem)
 		cmem->nr_ranges++;
 	}
 
+	for (i = 0; i < crashk_cma_cnt; i++) {
+		cmem->ranges[cmem->nr_ranges].start = crashk_cma_ranges[i].start;
+		cmem->ranges[cmem->nr_ranges].end = crashk_cma_ranges[i].end;
+		cmem->nr_ranges++;
+	}
+
 	return 0;
 }
 #endif
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 96711b8578fd..144e30fe9a75 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -96,8 +96,8 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
 
 static void __init arch_reserve_crashkernel(void)
 {
+	unsigned long long crash_base, crash_size, cma_size = 0;
 	unsigned long long low_size = 0;
-	unsigned long long crash_base, crash_size;
 	bool high = false;
 	int ret;
 
@@ -106,11 +106,12 @@ static void __init arch_reserve_crashkernel(void)
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base,
-				&low_size, NULL, &high);
+				&low_size, &cma_size, &high);
 	if (ret)
 		return;
 
 	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
+	reserve_crashkernel_cma(cma_size);
 }
 
 static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
-- 
2.34.1

[PATCH v6 5/5] riscv: kexec: Add support for crashkernel CMA reservation

[Jinjie Ruan]

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. This allows the kernel to dynamically allocate
contiguous memory for crash dumping when needed, rather than permanently
reserving a fixed region at boot time.

So extend crashkernel CMA reservation support to riscv. The following
changes are made to enable CMA reservation:

- 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 for kdump kernel to use.
- Exclude the CMA-reserved ranges from the crash kernel memory to
  prevent them from being exported through /proc/vmcore, which is already
  done in the crash core.

Update kernel-parameters.txt to document CMA support for crashkernel on
riscv architecture.

Acked-by: Paul Walmsley <pjw@kernel.org> # arch/riscv
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 16 ++++++++--------
 arch/riscv/kernel/machine_kexec_file.c          | 16 ++++++++++++++--
 arch/riscv/mm/init.c                            |  5 +++--
 3 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 497f63b76898..3f9ca148167e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1121,14 +1121,14 @@ Kernel parameters
 			It will be ignored when crashkernel=X,high is not used
 			or memory reserved is below 4G.
 	crashkernel=size[KMG],cma
-			[KNL, X86, ARM64, ppc] Reserve additional crash kernel memory from
-			CMA. This reservation is usable by the first system's
-			userspace memory and kernel movable allocations (memory
-			balloon, zswap). Pages allocated from this memory range
-			will not be included in the vmcore so this should not
-			be used if dumping of userspace memory is intended and
-			it has to be expected that some movable kernel pages
-			may be missing from the dump.
+			[KNL, X86, ARM64, RISCV, ppc] Reserve additional crash
+			kernel memory from CMA. This reservation is usable by
+			the first system's userspace memory and kernel movable
+			allocations (memory balloon, zswap). Pages allocated
+			from this memory range will not be included in the vmcore
+			so this should not be used if dumping of userspace memory
+			is intended and it has to be expected that some movable
+			kernel pages may be missing from the dump.
 
 			A standard crashkernel reservation, as described above,
 			is still needed to hold the crash kernel and initrd.
diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index d0e331d87155..605903e21c01 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -46,7 +46,7 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 
 unsigned int arch_get_system_nr_ranges(void)
 {
-	unsigned int nr_ranges = 1; /* For exclusion of crashkernel region */
+	unsigned int nr_ranges = 1 + crashk_cma_cnt; /* For exclusion of crashkernel region */
 
 	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
 
@@ -66,8 +66,20 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 
 int arch_crash_populate_cmem(struct crash_mem *cmem)
 {
+	int ret, i;
+
 	cmem->nr_ranges = 0;
-	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
+	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < crashk_cma_cnt; i++) {
+		cmem->ranges[cmem->nr_ranges].start = crashk_cma_ranges[i].start;
+		cmem->ranges[cmem->nr_ranges].end = crashk_cma_ranges[i].end;
+		cmem->nr_ranges++;
+	}
+
+	return 0;
 }
 
 static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 811e03786c56..4cd49afa9077 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1398,7 +1398,7 @@ static inline void setup_vm_final(void)
  */
 static void __init arch_reserve_crashkernel(void)
 {
-	unsigned long long low_size = 0;
+	unsigned long long low_size = 0, cma_size = 0;
 	unsigned long long crash_base, crash_size;
 	bool high = false;
 	int ret;
@@ -1408,11 +1408,12 @@ static void __init arch_reserve_crashkernel(void)
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base,
-				&low_size, NULL, &high);
+				&low_size, &cma_size, &high);
 	if (ret)
 		return;
 
 	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
+	reserve_crashkernel_cma(cma_size);
 }
 
 void __init paging_init(void)
-- 
2.34.1

Re: [PATCH v6 1/5] powerpc/crash: sort crash memory ranges before preparing elfcorehdr

[Ritesh Harjani]

Jinjie Ruan <ruanjinjie@huawei.com> writes:

> From: Sourabh Jain <sourabhjain@linux.ibm.com>
>
> During a memory hot-remove event, the elfcorehdr is rebuilt to exclude
> the removed memory. While updating the crash memory ranges for this
> operation, the crash memory ranges array can become unsorted. This
> happens because remove_mem_range() may split a memory range into two
> parts and append the higher-address part as a separate range at the end
> of the array.
>
> So far, no issues have been observed due to the unsorted crash memory
> ranges. However, this could lead to problems once crash memory range
> removal is handled by generic code, as introduced in the upcoming
> patches in this series.
>
> Currently, powerpc uses a platform-specific function,
> remove_mem_range(), to exclude hot-removed memory from the crash memory
> ranges. This function performs the same task as the generic
> crash_exclude_mem_range() in crash_core.c. The generic helper also
> ensures that the crash memory ranges remain sorted. So remove the
> redundant powerpc-specific implementation and instead call
> crash_exclude_mem_range_guarded() (which internally calls
> crash_exclude_mem_range()) to exclude the hot-removed memory ranges.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Baoquan he <bhe@redhat.com>
> Cc: Jinjie Ruan <ruanjinjie@huawei.com>
> Cc: Hari Bathini <hbathini@linux.ibm.com>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
> Cc: linux-kernel@vger.kernel.org
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>


I had gone through the generic implementation v/s the powerpc specific
remove_mem_range() implementation, when it was posted by Sourabh
separately. And it make sense to use the generic implementation in this
case, rather than keeping a duplicate powerpc specific version. So...

LGTM. Please feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Re: [PATCH v6 4/5] arm64: kexec: Add support for crashkernel CMA reservation

[Mike Rapoport]

On Tue, Feb 24, 2026 at 04:53:41PM +0800, Jinjie Ruan wrote:
> 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.
> 
> Crash kernel memory reservation wastes production resources if too
> large, risks kdump failure if too small, and faces allocation difficulties
> on fragmented systems due to contiguous block constraints. The new
> CMA-based crashkernel reservation scheme splits the "large fixed
> reservation" into a "small fixed region + large CMA dynamic region": the
> CMA memory is available to userspace during normal operation to avoid
> waste, and is reclaimed for kdump upon crash—saving memory while
> improving reliability.
> 
> So extend crashkernel CMA reservation support to arm64. The following
> changes are made to enable CMA reservation:
> 
> - 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 for kdump kernel to use.
> - Exclude the CMA-reserved ranges from the crash kernel memory to
>   prevent them from being exported through /proc/vmcore, which is already
>   done in the crash core.
> 
> Update kernel-parameters.txt to document CMA support for crashkernel on
> arm64 architecture.
> 
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
> v3:
> - Add Acked-by.
> v2:
> - Free cmem in prepare_elf_headers()
> - Add the mtivation.
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 2 +-
>  arch/arm64/kernel/machine_kexec_file.c          | 8 +++++++-
>  arch/arm64/mm/init.c                            | 5 +++--
>  3 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index cb850e5290c2..497f63b76898 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1121,7 +1121,7 @@ Kernel parameters
>  			It will be ignored when crashkernel=X,high is not used
>  			or memory reserved is below 4G.
>  	crashkernel=size[KMG],cma
> -			[KNL, X86, ppc] Reserve additional crash kernel memory from
> +			[KNL, X86, ARM64, ppc] Reserve additional crash kernel memory from
>  			CMA. This reservation is usable by the first system's
>  			userspace memory and kernel movable allocations (memory
>  			balloon, zswap). Pages allocated from this memory range
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> index c338506a580b..c8862a762eb3 100644
> --- a/arch/arm64/kernel/machine_kexec_file.c
> +++ b/arch/arm64/kernel/machine_kexec_file.c
> @@ -42,7 +42,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
>  #ifdef CONFIG_CRASH_DUMP
>  unsigned int arch_get_system_nr_ranges(void)
>  {
> -	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
> +	unsigned int nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */
>  	phys_addr_t start, end;
>  	u64 i;
>  
> @@ -64,6 +64,12 @@ int arch_crash_populate_cmem(struct crash_mem *cmem)
>  		cmem->nr_ranges++;
>  	}
>  
> +	for (i = 0; i < crashk_cma_cnt; i++) {
> +		cmem->ranges[cmem->nr_ranges].start = crashk_cma_ranges[i].start;
> +		cmem->ranges[cmem->nr_ranges].end = crashk_cma_ranges[i].end;
> +		cmem->nr_ranges++;
> +	}

Why do we need to add cma ranges here? They are anyway will be excluded in
crash_exclude_core_ranges().

The same comment applies to riscv patch.

>  	return 0;
>  }
>  #endif
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 96711b8578fd..144e30fe9a75 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -96,8 +96,8 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
>  
>  static void __init arch_reserve_crashkernel(void)
>  {
> +	unsigned long long crash_base, crash_size, cma_size = 0;
>  	unsigned long long low_size = 0;
> -	unsigned long long crash_base, crash_size;
>  	bool high = false;
>  	int ret;
>  
> @@ -106,11 +106,12 @@ static void __init arch_reserve_crashkernel(void)
>  
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  				&crash_size, &crash_base,
> -				&low_size, NULL, &high);
> +				&low_size, &cma_size, &high);
>  	if (ret)
>  		return;
>  
>  	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
> +	reserve_crashkernel_cma(cma_size);
>  }
>  
>  static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
> -- 
> 2.34.1
> 

-- 
Sincerely yours,
Mike.

Re: [PATCH v6 0/5] arm64/riscv: Add support for crashkernel CMA reservation

[Mike Rapoport]

On Tue, Feb 24, 2026 at 04:53:37PM +0800, Jinjie Ruan wrote:
> The crash memory allocation, and the exclude of crashk_res, crashk_low_res
> and crashk_cma memory are almost identical across different architectures,
> This patch set handle them in crash core in a general way, which eliminate
> a lot of duplication code.
> 
> And add support for crashkernel CMA reservation for arm64 and riscv.
> 
> Rebased on v7.0-rc1.
> 
> Basic test were performed on QEMU platforms for x86, ARM64, and RISC-V
> architectures with the following parameters:
> 
> 	"cma=256M crashkernel=256M crashkernel=64M,cma"
> 
> Changes in v6:
> - Update the crash core exclude code as Mike suggested.
> - Rebased on v7.0-rc1.
> - Add acked-by.
> - Link to v5: https://lore.kernel.org/all/20260212101001.343158-1-ruanjinjie@huawei.com/
> 
> Changes in v5:
> - Fix the kernel test robot build warnings.
> - Sort crash memory ranges before preparing elfcorehdr for powerpc
> - Link to v4: https://lore.kernel.org/all/20260209095931.2813152-1-ruanjinjie@huawei.com/
> 
> Changes in v4:
> - Move the size calculation (and the realloc if needed) into the
>   generic crash.
> - Link to v3: https://lore.kernel.org/all/20260204093728.1447527-1-ruanjinjie@huawei.com/
> 
> Changs in v3:
> - Exclude crash kernel memory in crash core as Mike suggested.
> - Add acked-by.
> 
> Jinjie Ruan (4):
>   crash: Exclude crash kernel memory in crash core
>   crash: Use crash_exclude_core_ranges() on powerpc
>   arm64: kexec: Add support for crashkernel CMA reservation
>   riscv: kexec: Add support for crashkernel CMA reservation
> 
> Sourabh Jain (1):
>   powerpc/crash: sort crash memory ranges before preparing elfcorehdr

Overall LGTM, I had a comment about arm64 and riscv patches, but other than
that

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

-- 
Sincerely yours,
Mike.

Re: [PATCH v6 4/5] arm64: kexec: Add support for crashkernel CMA reservation

[Jinjie Ruan]

On 2026/2/25 23:48, Mike Rapoport wrote:
> On Tue, Feb 24, 2026 at 04:53:41PM +0800, Jinjie Ruan wrote:
>> 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.
>>
>> Crash kernel memory reservation wastes production resources if too
>> large, risks kdump failure if too small, and faces allocation difficulties
>> on fragmented systems due to contiguous block constraints. The new
>> CMA-based crashkernel reservation scheme splits the "large fixed
>> reservation" into a "small fixed region + large CMA dynamic region": the
>> CMA memory is available to userspace during normal operation to avoid
>> waste, and is reclaimed for kdump upon crash—saving memory while
>> improving reliability.
>>
>> So extend crashkernel CMA reservation support to arm64. The following
>> changes are made to enable CMA reservation:
>>
>> - 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 for kdump kernel to use.
>> - Exclude the CMA-reserved ranges from the crash kernel memory to
>>   prevent them from being exported through /proc/vmcore, which is already
>>   done in the crash core.
>>
>> Update kernel-parameters.txt to document CMA support for crashkernel on
>> arm64 architecture.
>>
>> Acked-by: Ard Biesheuvel <ardb@kernel.org>
>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
>> ---
>> v3:
>> - Add Acked-by.
>> v2:
>> - Free cmem in prepare_elf_headers()
>> - Add the mtivation.
>> ---
>>  Documentation/admin-guide/kernel-parameters.txt | 2 +-
>>  arch/arm64/kernel/machine_kexec_file.c          | 8 +++++++-
>>  arch/arm64/mm/init.c                            | 5 +++--
>>  3 files changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index cb850e5290c2..497f63b76898 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -1121,7 +1121,7 @@ Kernel parameters
>>  			It will be ignored when crashkernel=X,high is not used
>>  			or memory reserved is below 4G.
>>  	crashkernel=size[KMG],cma
>> -			[KNL, X86, ppc] Reserve additional crash kernel memory from
>> +			[KNL, X86, ARM64, ppc] Reserve additional crash kernel memory from
>>  			CMA. This reservation is usable by the first system's
>>  			userspace memory and kernel movable allocations (memory
>>  			balloon, zswap). Pages allocated from this memory range
>> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
>> index c338506a580b..c8862a762eb3 100644
>> --- a/arch/arm64/kernel/machine_kexec_file.c
>> +++ b/arch/arm64/kernel/machine_kexec_file.c
>> @@ -42,7 +42,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
>>  #ifdef CONFIG_CRASH_DUMP
>>  unsigned int arch_get_system_nr_ranges(void)
>>  {
>> -	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
>> +	unsigned int nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */
>>  	phys_addr_t start, end;
>>  	u64 i;
>>  
>> @@ -64,6 +64,12 @@ int arch_crash_populate_cmem(struct crash_mem *cmem)
>>  		cmem->nr_ranges++;
>>  	}
>>  
>> +	for (i = 0; i < crashk_cma_cnt; i++) {
>> +		cmem->ranges[cmem->nr_ranges].start = crashk_cma_ranges[i].start;
>> +		cmem->ranges[cmem->nr_ranges].end = crashk_cma_ranges[i].end;
>> +		cmem->nr_ranges++;
>> +	}
> 
> Why do we need to add cma ranges here? They are anyway will be excluded in
> crash_exclude_core_ranges().
> 
> The same comment applies to riscv patch.

Indeed, it should not be placed here. In the kexec DT code, these memory
regions need to be included in the "usable-memory-range",which is
equivalent to the x86 crash_setup_memmap_entries() function.

> 
>>  	return 0;
>>  }
>>  #endif
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 96711b8578fd..144e30fe9a75 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -96,8 +96,8 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
>>  
>>  static void __init arch_reserve_crashkernel(void)
>>  {
>> +	unsigned long long crash_base, crash_size, cma_size = 0;
>>  	unsigned long long low_size = 0;
>> -	unsigned long long crash_base, crash_size;
>>  	bool high = false;
>>  	int ret;
>>  
>> @@ -106,11 +106,12 @@ static void __init arch_reserve_crashkernel(void)
>>  
>>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>>  				&crash_size, &crash_base,
>> -				&low_size, NULL, &high);
>> +				&low_size, &cma_size, &high);
>>  	if (ret)
>>  		return;
>>  
>>  	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
>> +	reserve_crashkernel_cma(cma_size);
>>  }
>>  
>>  static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
>> -- 
>> 2.34.1
>>
> 

Re: [PATCH v6 1/5] powerpc/crash: sort crash memory ranges before preparing elfcorehdr

[Baoquan He]

On 02/24/26 at 04:53pm, Jinjie Ruan wrote:
> From: Sourabh Jain <sourabhjain@linux.ibm.com>
> 
> During a memory hot-remove event, the elfcorehdr is rebuilt to exclude
> the removed memory. While updating the crash memory ranges for this
> operation, the crash memory ranges array can become unsorted. This
> happens because remove_mem_range() may split a memory range into two
> parts and append the higher-address part as a separate range at the end
> of the array.
> 
> So far, no issues have been observed due to the unsorted crash memory
> ranges. However, this could lead to problems once crash memory range
> removal is handled by generic code, as introduced in the upcoming
> patches in this series.
> 
> Currently, powerpc uses a platform-specific function,
> remove_mem_range(), to exclude hot-removed memory from the crash memory
> ranges. This function performs the same task as the generic
> crash_exclude_mem_range() in crash_core.c. The generic helper also
> ensures that the crash memory ranges remain sorted. So remove the
> redundant powerpc-specific implementation and instead call
> crash_exclude_mem_range_guarded() (which internally calls
> crash_exclude_mem_range()) to exclude the hot-removed memory ranges.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Baoquan he <bhe@redhat.com>
> Cc: Jinjie Ruan <ruanjinjie@huawei.com>
> Cc: Hari Bathini <hbathini@linux.ibm.com>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
> Cc: linux-kernel@vger.kernel.org
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>

You should add your own Signed-off-by since you sent it out.

> ---
>  arch/powerpc/include/asm/kexec_ranges.h |  4 +-
>  arch/powerpc/kexec/crash.c              |  5 +-
>  arch/powerpc/kexec/ranges.c             | 87 +------------------------
>  3 files changed, 7 insertions(+), 89 deletions(-)
......snip...

Re: [PATCH v6 2/5] crash: Exclude crash kernel memory in crash core

[Baoquan He]

On 02/24/26 at 04:53pm, Jinjie Ruan wrote:
> The crash memory alloc, and the exclude of crashk_res, crashk_low_res
> and crashk_cma memory are almost identical across different architectures,
> handling them in the crash core would eliminate a lot of duplication, so
> do them in the common code.
> 
> To achieve the above goal, three architecture-specific functions are
> introduced:
> 
> - arch_get_system_nr_ranges(). Pre-counts the max number of memory ranges.
> 
> - arch_crash_populate_cmem(). Collects the memory ranges and fills them
>   into cmem.
> 
> - arch_crash_exclude_ranges(). Architecture's additional crash memory
>   ranges exclusion, defaulting to empty.
> 
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>  arch/arm64/kernel/machine_kexec_file.c     | 39 +++-------
>  arch/loongarch/kernel/machine_kexec_file.c | 39 +++-------
>  arch/riscv/kernel/machine_kexec_file.c     | 38 +++------
>  arch/x86/kernel/crash.c                    | 89 +++-------------------
>  include/linux/crash_core.h                 |  5 ++
>  kernel/crash_core.c                        | 82 +++++++++++++++++++-
>  6 files changed, 132 insertions(+), 160 deletions(-)

LGTM,

Acked-by: Baoquan He <bhe@redhat.com>

> 
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> index fba260ad87a9..c338506a580b 100644
> --- a/arch/arm64/kernel/machine_kexec_file.c
> +++ b/arch/arm64/kernel/machine_kexec_file.c
> @@ -40,23 +40,23 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
>  }
>  
>  #ifdef CONFIG_CRASH_DUMP
> -static int prepare_elf_headers(void **addr, unsigned long *sz)
> +unsigned int arch_get_system_nr_ranges(void)
>  {
> -	struct crash_mem *cmem;
> -	unsigned int nr_ranges;
> -	int ret;
> -	u64 i;
> +	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
>  	phys_addr_t start, end;
> +	u64 i;
>  
> -	nr_ranges = 2; /* for exclusion of crashkernel region */
>  	for_each_mem_range(i, &start, &end)
>  		nr_ranges++;
>  
> -	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
> -	if (!cmem)
> -		return -ENOMEM;
> +	return nr_ranges;
> +}
> +
> +int arch_crash_populate_cmem(struct crash_mem *cmem)
> +{
> +	phys_addr_t start, end;
> +	u64 i;
>  
> -	cmem->max_nr_ranges = nr_ranges;
>  	cmem->nr_ranges = 0;
>  	for_each_mem_range(i, &start, &end) {
>  		cmem->ranges[cmem->nr_ranges].start = start;
> @@ -64,22 +64,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
>  		cmem->nr_ranges++;
>  	}
>  
> -	/* Exclude crashkernel region */
> -	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> -	if (ret)
> -		goto out;
> -
> -	if (crashk_low_res.end) {
> -		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
> -		if (ret)
> -			goto out;
> -	}
> -
> -	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
> -
> -out:
> -	kfree(cmem);
> -	return ret;
> +	return 0;
>  }
>  #endif
>  
> @@ -109,7 +94,7 @@ int load_other_segments(struct kimage *image,
>  	void *headers;
>  	unsigned long headers_sz;
>  	if (image->type == KEXEC_TYPE_CRASH) {
> -		ret = prepare_elf_headers(&headers, &headers_sz);
> +		ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
>  		if (ret) {
>  			pr_err("Preparing elf core header failed\n");
>  			goto out_err;
> diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
> index 5584b798ba46..4b318a94b564 100644
> --- a/arch/loongarch/kernel/machine_kexec_file.c
> +++ b/arch/loongarch/kernel/machine_kexec_file.c
> @@ -56,23 +56,23 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
>  }
>  
>  #ifdef CONFIG_CRASH_DUMP
> -
> -static int prepare_elf_headers(void **addr, unsigned long *sz)
> +unsigned int arch_get_system_nr_ranges(void)
>  {
> -	int ret, nr_ranges;
> -	uint64_t i;
> +	int nr_ranges = 2; /* for exclusion of crashkernel region */
>  	phys_addr_t start, end;
> -	struct crash_mem *cmem;
> +	uint64_t i;
>  
> -	nr_ranges = 2; /* for exclusion of crashkernel region */
>  	for_each_mem_range(i, &start, &end)
>  		nr_ranges++;
>  
> -	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
> -	if (!cmem)
> -		return -ENOMEM;
> +	return nr_ranges;
> +}
> +
> +int arch_crash_populate_cmem(struct crash_mem *cmem)
> +{
> +	phys_addr_t start, end;
> +	uint64_t i;
>  
> -	cmem->max_nr_ranges = nr_ranges;
>  	cmem->nr_ranges = 0;
>  	for_each_mem_range(i, &start, &end) {
>  		cmem->ranges[cmem->nr_ranges].start = start;
> @@ -80,22 +80,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
>  		cmem->nr_ranges++;
>  	}
>  
> -	/* Exclude crashkernel region */
> -	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> -	if (ret < 0)
> -		goto out;
> -
> -	if (crashk_low_res.end) {
> -		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
> -		if (ret < 0)
> -			goto out;
> -	}
> -
> -	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
> -
> -out:
> -	kfree(cmem);
> -	return ret;
> +	return 0;
>  }
>  
>  /*
> @@ -163,7 +148,7 @@ int load_other_segments(struct kimage *image,
>  		void *headers;
>  		unsigned long headers_sz;
>  
> -		ret = prepare_elf_headers(&headers, &headers_sz);
> +		ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
>  		if (ret < 0) {
>  			pr_err("Preparing elf core header failed\n");
>  			goto out_err;
> diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
> index 54e2d9552e93..d0e331d87155 100644
> --- a/arch/riscv/kernel/machine_kexec_file.c
> +++ b/arch/riscv/kernel/machine_kexec_file.c
> @@ -44,6 +44,15 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
>  	return 0;
>  }
>  
> +unsigned int arch_get_system_nr_ranges(void)
> +{
> +	unsigned int nr_ranges = 1; /* For exclusion of crashkernel region */
> +
> +	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
> +
> +	return nr_ranges;
> +}
> +
>  static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>  {
>  	struct crash_mem *cmem = arg;
> @@ -55,33 +64,10 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>  	return 0;
>  }
>  
> -static int prepare_elf_headers(void **addr, unsigned long *sz)
> +int arch_crash_populate_cmem(struct crash_mem *cmem)
>  {
> -	struct crash_mem *cmem;
> -	unsigned int nr_ranges;
> -	int ret;
> -
> -	nr_ranges = 1; /* For exclusion of crashkernel region */
> -	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
> -
> -	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
> -	if (!cmem)
> -		return -ENOMEM;
> -
> -	cmem->max_nr_ranges = nr_ranges;
>  	cmem->nr_ranges = 0;
> -	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
> -	if (ret)
> -		goto out;
> -
> -	/* Exclude crashkernel region */
> -	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> -	if (!ret)
> -		ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
> -
> -out:
> -	kfree(cmem);
> -	return ret;
> +	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
>  }
>  
>  static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
> @@ -273,7 +259,7 @@ int load_extra_segments(struct kimage *image, unsigned long kernel_start,
>  	if (image->type == KEXEC_TYPE_CRASH) {
>  		void *headers;
>  		unsigned long headers_sz;
> -		ret = prepare_elf_headers(&headers, &headers_sz);
> +		ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
>  		if (ret) {
>  			pr_err("Preparing elf core header failed\n");
>  			goto out;
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 335fd2ee9766..3ad3f8b758a4 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -152,16 +152,8 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
>  	return 0;
>  }
>  
> -/* Gather all the required information to prepare elf headers for ram regions */
> -static struct crash_mem *fill_up_crash_elf_data(void)
> +unsigned int arch_get_system_nr_ranges(void)
>  {
> -	unsigned int nr_ranges = 0;
> -	struct crash_mem *cmem;
> -
> -	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
> -	if (!nr_ranges)
> -		return NULL;
> -
>  	/*
>  	 * Exclusion of crash region, crashk_low_res and/or crashk_cma_ranges
>  	 * may cause range splits. So add extra slots here.
> @@ -176,49 +168,16 @@ static struct crash_mem *fill_up_crash_elf_data(void)
>  	 * But in order to lest the low 1M could be changed in the future,
>  	 * (e.g. [start, 1M]), add a extra slot.
>  	 */
> -	nr_ranges += 3 + crashk_cma_cnt;
> -	cmem = vzalloc(struct_size(cmem, ranges, nr_ranges));
> -	if (!cmem)
> -		return NULL;
> -
> -	cmem->max_nr_ranges = nr_ranges;
> +	unsigned int nr_ranges = 3 + crashk_cma_cnt;
>  
> -	return cmem;
> +	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
> +	return nr_ranges;
>  }
>  
> -/*
> - * Look for any unwanted ranges between mstart, mend and remove them. This
> - * might lead to split and split ranges are put in cmem->ranges[] array
> - */
> -static int elf_header_exclude_ranges(struct crash_mem *cmem)
> +int arch_crash_exclude_ranges(struct crash_mem *cmem)
>  {
> -	int ret = 0;
> -	int i;
> -
>  	/* Exclude the low 1M because it is always reserved */
> -	ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
> -	if (ret)
> -		return ret;
> -
> -	/* Exclude crashkernel region */
> -	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> -	if (ret)
> -		return ret;
> -
> -	if (crashk_low_res.end)
> -		ret = crash_exclude_mem_range(cmem, crashk_low_res.start,
> -					      crashk_low_res.end);
> -	if (ret)
> -		return ret;
> -
> -	for (i = 0; i < crashk_cma_cnt; ++i) {
> -		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
> -					      crashk_cma_ranges[i].end);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	return 0;
> +	return crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
>  }
>  
>  static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
> @@ -232,35 +191,9 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>  	return 0;
>  }
>  
> -/* Prepare elf headers. Return addr and size */
> -static int prepare_elf_headers(void **addr, unsigned long *sz,
> -			       unsigned long *nr_mem_ranges)
> +int arch_crash_populate_cmem(struct crash_mem *cmem)
>  {
> -	struct crash_mem *cmem;
> -	int ret;
> -
> -	cmem = fill_up_crash_elf_data();
> -	if (!cmem)
> -		return -ENOMEM;
> -
> -	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
> -	if (ret)
> -		goto out;
> -
> -	/* Exclude unwanted mem ranges */
> -	ret = elf_header_exclude_ranges(cmem);
> -	if (ret)
> -		goto out;
> -
> -	/* Return the computed number of memory ranges, for hotplug usage */
> -	*nr_mem_ranges = cmem->nr_ranges;
> -
> -	/* By default prepare 64bit headers */
> -	ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
> -
> -out:
> -	vfree(cmem);
> -	return ret;
> +	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
>  }
>  #endif
>  
> @@ -418,7 +351,8 @@ int crash_load_segments(struct kimage *image)
>  				  .buf_max = ULONG_MAX, .top_down = false };
>  
>  	/* Prepare elf headers and add a segment */
> -	ret = prepare_elf_headers(&kbuf.buffer, &kbuf.bufsz, &pnum);
> +	ret = crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &kbuf.buffer,
> +				    &kbuf.bufsz, &pnum);
>  	if (ret)
>  		return ret;
>  
> @@ -529,7 +463,8 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
>  	 * Create the new elfcorehdr reflecting the changes to CPU and/or
>  	 * memory resources.
>  	 */
> -	if (prepare_elf_headers(&elfbuf, &elfsz, &nr_mem_ranges)) {
> +	if (crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz,
> +				  &nr_mem_ranges)) {
>  		pr_err("unable to create new elfcorehdr");
>  		goto out;
>  	}
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index d35726d6a415..033b20204aca 100644
> --- a/include/linux/crash_core.h
> +++ b/include/linux/crash_core.h
> @@ -66,6 +66,8 @@ extern int crash_exclude_mem_range(struct crash_mem *mem,
>  				   unsigned long long mend);
>  extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>  				       void **addr, unsigned long *sz);
> +extern int crash_prepare_headers(int need_kernel_map, void **addr,
> +				 unsigned long *sz, unsigned long *nr_mem_ranges);
>  
>  struct kimage;
>  struct kexec_segment;
> @@ -83,6 +85,9 @@ int kexec_should_crash(struct task_struct *p);
>  int kexec_crash_loaded(void);
>  void crash_save_cpu(struct pt_regs *regs, int cpu);
>  extern int kimage_crash_copy_vmcoreinfo(struct kimage *image);
> +extern unsigned int arch_get_system_nr_ranges(void);
> +extern int arch_crash_populate_cmem(struct crash_mem *cmem);
> +extern int arch_crash_exclude_ranges(struct crash_mem *cmem);
>  
>  #else /* !CONFIG_CRASH_DUMP*/
>  struct pt_regs;
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 2c1a3791e410..96a96e511f5a 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -170,9 +170,6 @@ static inline resource_size_t crash_resource_size(const struct resource *res)
>  	return !res->end ? 0 : resource_size(res);
>  }
>  
> -
> -
> -
>  int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>  			  void **addr, unsigned long *sz)
>  {
> @@ -274,6 +271,85 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>  	return 0;
>  }
>  
> +static struct crash_mem *alloc_cmem(unsigned int nr_ranges)
> +{
> +	struct crash_mem *cmem;
> +
> +	cmem = kvzalloc_flex(*cmem, ranges, nr_ranges);
> +	if (!cmem)
> +		return NULL;
> +
> +	cmem->max_nr_ranges = nr_ranges;
> +	return cmem;
> +}
> +
> +unsigned int __weak arch_get_system_nr_ranges(void) { return 0; }
> +int __weak arch_crash_populate_cmem(struct crash_mem *cmem) { return -1; }
> +int __weak arch_crash_exclude_ranges(struct crash_mem *cmem) { return 0; }
> +
> +static int crash_exclude_core_ranges(struct crash_mem *cmem)
> +{
> +	int ret, i;
> +
> +	/* Exclude crashkernel region */
> +	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> +	if (ret)
> +		return ret;
> +
> +	if (crashk_low_res.end) {
> +		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	for (i = 0; i < crashk_cma_cnt; ++i) {
> +		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
> +					      crashk_cma_ranges[i].end);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz,
> +			  unsigned long *nr_mem_ranges)
> +{
> +	unsigned int max_nr_ranges;
> +	struct crash_mem *cmem;
> +	int ret;
> +
> +	max_nr_ranges = arch_get_system_nr_ranges();
> +	if (!max_nr_ranges)
> +		return -ENOMEM;
> +
> +	cmem = alloc_cmem(max_nr_ranges);
> +	if (!cmem)
> +		return -ENOMEM;
> +
> +	ret = arch_crash_populate_cmem(cmem);
> +	if (ret)
> +		goto out;
> +
> +	ret = crash_exclude_core_ranges(cmem);
> +	if (ret)
> +		goto out;
> +
> +	ret = arch_crash_exclude_ranges(cmem);
> +	if (ret)
> +		goto out;
> +
> +	/* Return the computed number of memory ranges, for hotplug usage */
> +	if (nr_mem_ranges)
> +		*nr_mem_ranges = cmem->nr_ranges;
> +
> +	ret = crash_prepare_elf64_headers(cmem, need_kernel_map, addr, sz);
> +
> +out:
> +	kvfree(cmem);
> +	return ret;
> +}
> +
>  /**
>   * crash_exclude_mem_range - exclude a mem range for existing ranges
>   * @mem: mem->range contains an array of ranges sorted in ascending order
> -- 
> 2.34.1
> 

Re: [PATCH v6 4/5] arm64: kexec: Add support for crashkernel CMA reservation

[Baoquan He]

On 02/24/26 at 04:53pm, Jinjie Ruan wrote:
> 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.
> 
> Crash kernel memory reservation wastes production resources if too
> large, risks kdump failure if too small, and faces allocation difficulties
> on fragmented systems due to contiguous block constraints. The new
> CMA-based crashkernel reservation scheme splits the "large fixed
> reservation" into a "small fixed region + large CMA dynamic region": the
> CMA memory is available to userspace during normal operation to avoid
> waste, and is reclaimed for kdump upon crash—saving memory while
> improving reliability.
> 
> So extend crashkernel CMA reservation support to arm64. The following
> changes are made to enable CMA reservation:
> 
> - 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 for kdump kernel to use.
> - Exclude the CMA-reserved ranges from the crash kernel memory to
>   prevent them from being exported through /proc/vmcore, which is already
>   done in the crash core.
> 
> Update kernel-parameters.txt to document CMA support for crashkernel on
> arm64 architecture.
> 
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
> v3:
> - Add Acked-by.
> v2:
> - Free cmem in prepare_elf_headers()
> - Add the mtivation.
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 2 +-
>  arch/arm64/kernel/machine_kexec_file.c          | 8 +++++++-
>  arch/arm64/mm/init.c                            | 5 +++--
>  3 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index cb850e5290c2..497f63b76898 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1121,7 +1121,7 @@ Kernel parameters
>  			It will be ignored when crashkernel=X,high is not used
>  			or memory reserved is below 4G.
>  	crashkernel=size[KMG],cma
> -			[KNL, X86, ppc] Reserve additional crash kernel memory from
> +			[KNL, X86, ARM64, ppc] Reserve additional crash kernel memory from
                                          ~~~~ 
This should be written as 'PPC', even though it's not introduced in this patch.
===
 PPC     PowerPC architecture is enabled.
===

Other than this nit, the overral looks good to me.

>  			CMA. This reservation is usable by the first system's
>  			userspace memory and kernel movable allocations (memory
>  			balloon, zswap). Pages allocated from this memory range
......snip...

Re: [PATCH v6 1/5] powerpc/crash: sort crash memory ranges before preparing elfcorehdr

[Jinjie Ruan]

On 2026/2/26 17:24, Baoquan He wrote:
> On 02/24/26 at 04:53pm, Jinjie Ruan wrote:
>> From: Sourabh Jain <sourabhjain@linux.ibm.com>
>>
>> During a memory hot-remove event, the elfcorehdr is rebuilt to exclude
>> the removed memory. While updating the crash memory ranges for this
>> operation, the crash memory ranges array can become unsorted. This
>> happens because remove_mem_range() may split a memory range into two
>> parts and append the higher-address part as a separate range at the end
>> of the array.
>>
>> So far, no issues have been observed due to the unsorted crash memory
>> ranges. However, this could lead to problems once crash memory range
>> removal is handled by generic code, as introduced in the upcoming
>> patches in this series.
>>
>> Currently, powerpc uses a platform-specific function,
>> remove_mem_range(), to exclude hot-removed memory from the crash memory
>> ranges. This function performs the same task as the generic
>> crash_exclude_mem_range() in crash_core.c. The generic helper also
>> ensures that the crash memory ranges remain sorted. So remove the
>> redundant powerpc-specific implementation and instead call
>> crash_exclude_mem_range_guarded() (which internally calls
>> crash_exclude_mem_range()) to exclude the hot-removed memory ranges.
>>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Baoquan he <bhe@redhat.com>
>> Cc: Jinjie Ruan <ruanjinjie@huawei.com>
>> Cc: Hari Bathini <hbathini@linux.ibm.com>
>> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
>> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>> Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
>> Cc: linux-kernel@vger.kernel.org
>> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
>> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> 
> You should add your own Signed-off-by since you sent it out.

Ack, I'll add my Signed-off-by in the next revision.
Thanks,

> 
>> ---
>>  arch/powerpc/include/asm/kexec_ranges.h |  4 +-
>>  arch/powerpc/kexec/crash.c              |  5 +-
>>  arch/powerpc/kexec/ranges.c             | 87 +------------------------
>>  3 files changed, 7 insertions(+), 89 deletions(-)
> ......snip...
> 
>