[PATCH v3 0/3] arm64/riscv: Add support for crashkernel CMA reservation

[PATCH v3 0/3] arm64/riscv: Add support for crashkernel CMA reservation

[Jinjie Ruan]

Add support for crashkernel CMA reservation for arm64 and riscv.

By the way, exclude crash kernel memory in crash core to
avoid duplication.

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

Jinjie Ruan (3):
  crash: Exclude crash kernel memory in crash core
  arm64: kexec: Add support for crashkernel CMA reservation
  riscv: kexec: Add support for crashkernel CMA reservation

 .../admin-guide/kernel-parameters.txt         | 16 ++++----
 arch/arm64/kernel/machine_kexec_file.c        | 16 +++-----
 arch/arm64/mm/init.c                          |  5 ++-
 arch/loongarch/kernel/machine_kexec_file.c    | 12 ------
 arch/powerpc/kexec/ranges.c                   | 16 ++------
 arch/riscv/kernel/machine_kexec_file.c        | 15 ++++---
 arch/riscv/mm/init.c                          |  5 ++-
 arch/x86/kernel/crash.c                       | 39 +------------------
 kernel/crash_core.c                           | 28 +++++++++++++
 9 files changed, 61 insertions(+), 91 deletions(-)

-- 
2.34.1

[PATCH v3 1/3] crash: Exclude crash kernel memory in crash core

[Jinjie Ruan]

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

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/machine_kexec_file.c     | 12 -------
 arch/loongarch/kernel/machine_kexec_file.c | 12 -------
 arch/powerpc/kexec/ranges.c                | 16 ++-------
 arch/riscv/kernel/machine_kexec_file.c     |  5 +--
 arch/x86/kernel/crash.c                    | 39 ++--------------------
 kernel/crash_core.c                        | 28 ++++++++++++++++
 6 files changed, 34 insertions(+), 78 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 410060ebd86d..ed2c45007158 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -64,20 +64,8 @@ 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;
 }
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index fb57026f5f25..26f867e53955 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -80,20 +80,8 @@ 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;
 }
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index 867135560e5c..3f76dd266b1f 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -553,9 +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,
-					   unsigned long long mstart,
-					   unsigned long long mend)
+static int crash_realloc_mem_range_guarded(struct crash_mem **mem_ranges)
 {
 	struct crash_mem *tmem = *mem_ranges;
 
@@ -566,7 +564,7 @@ static int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
 			return -ENOMEM;
 	}
 
-	return crash_exclude_mem_range(tmem, mstart, mend);
+	return 0;
 }
 
 /**
@@ -604,18 +602,10 @@ 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_realloc_mem_range_guarded(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/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index dd9d92a96517..fec3622a13c9 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -74,10 +74,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 	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);
+	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
 
 out:
 	kfree(cmem);
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 335fd2ee9766..d8341a48f6b3 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -186,41 +186,6 @@ static struct crash_mem *fill_up_crash_elf_data(void)
 	return cmem;
 }
 
-/*
- * 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 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;
-}
-
 static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 {
 	struct crash_mem *cmem = arg;
@@ -247,8 +212,8 @@ static int prepare_elf_headers(void **addr, unsigned long *sz,
 	if (ret)
 		goto out;
 
-	/* Exclude unwanted mem ranges */
-	ret = elf_header_exclude_ranges(cmem);
+	/* Exclude the low 1M because it is always reserved */
+	ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
 	if (ret)
 		goto out;
 
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 99dac1aa972a..5c0de111ddc3 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -18,6 +18,7 @@
 #include <linux/memblock.h>
 #include <linux/kmemleak.h>
 #include <linux/crash_core.h>
+#include <linux/crash_reserve.h>
 #include <linux/reboot.h>
 #include <linux/btf.h>
 #include <linux/objtool.h>
@@ -161,8 +162,30 @@ static inline resource_size_t crash_resource_size(const struct resource *res)
 	return !res->end ? 0 : resource_size(res);
 }
 
+static int crash_exclude_mem_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 ret;
+}
 
 int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 			  void **addr, unsigned long *sz)
@@ -174,6 +197,11 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 	unsigned int cpu, i;
 	unsigned long long notes_addr;
 	unsigned long mstart, mend;
+	int ret;
+
+	ret = crash_exclude_mem_ranges(mem);
+	if (ret)
+		return ret;
 
 	/* extra phdr for vmcoreinfo ELF note */
 	nr_phdr = nr_cpus + 1;
-- 
2.34.1

[PATCH v3 2/3] 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.

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 1058f2a6d6a8..36bb642a7edd 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1119,7 +1119,7 @@ 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 ed2c45007158..cab4aaf8cb22 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -48,7 +48,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 	u64 i;
 	phys_addr_t start, end;
 
-	nr_ranges = 2; /* for exclusion of crashkernel region */
+	nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */
 	for_each_mem_range(i, &start, &end)
 		nr_ranges++;
 
@@ -64,6 +64,12 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 		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++;
+	}
+
 	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
 
 	kfree(cmem);
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 524d34a0e921..28165d94af08 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 v3 3/3] 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.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 16 ++++++++--------
 arch/riscv/kernel/machine_kexec_file.c          | 10 ++++++++--
 arch/riscv/mm/init.c                            |  5 +++--
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 36bb642a7edd..3b92324d3a03 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1119,14 +1119,14 @@ 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 fec3622a13c9..0e4ac70d5a9a 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -59,9 +59,9 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 {
 	struct crash_mem *cmem;
 	unsigned int nr_ranges;
-	int ret;
+	int ret, i;
 
-	nr_ranges = 1; /* For exclusion of crashkernel region */
+	nr_ranges = 1 + crashk_cma_cnt; /* For exclusion of crashkernel region */
 	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
 
 	cmem = kmalloc(struct_size(cmem, ranges, nr_ranges), GFP_KERNEL);
@@ -74,6 +74,12 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 	if (ret)
 		goto out;
 
+	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++;
+	}
+
 	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
 
 out:
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index addb8a9305be..074d2d5f79ee 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1404,7 +1404,7 @@ 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;
@@ -1414,11 +1414,12 @@ 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 v3 1/3] crash: Exclude crash kernel memory in crash core

[Sourabh Jain]

On 04/02/26 15:07, Jinjie Ruan wrote:
> The exclude of crashk_res, crashk_low_res and crashk_cma memory
> are almost identical across different architectures, so handling them
> in the crash core would eliminate a lot of duplication, so do
> them in the common code.
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>   arch/arm64/kernel/machine_kexec_file.c     | 12 -------
>   arch/loongarch/kernel/machine_kexec_file.c | 12 -------
>   arch/powerpc/kexec/ranges.c                | 16 ++-------
>   arch/riscv/kernel/machine_kexec_file.c     |  5 +--
>   arch/x86/kernel/crash.c                    | 39 ++--------------------
>   kernel/crash_core.c                        | 28 ++++++++++++++++
>   6 files changed, 34 insertions(+), 78 deletions(-)
>
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> index 410060ebd86d..ed2c45007158 100644
> --- a/arch/arm64/kernel/machine_kexec_file.c
> +++ b/arch/arm64/kernel/machine_kexec_file.c
> @@ -64,20 +64,8 @@ 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;
>   }
> diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
> index fb57026f5f25..26f867e53955 100644
> --- a/arch/loongarch/kernel/machine_kexec_file.c
> +++ b/arch/loongarch/kernel/machine_kexec_file.c
> @@ -80,20 +80,8 @@ 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;
>   }
> diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
> index 867135560e5c..3f76dd266b1f 100644
> --- a/arch/powerpc/kexec/ranges.c
> +++ b/arch/powerpc/kexec/ranges.c
> @@ -553,9 +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,
> -					   unsigned long long mstart,
> -					   unsigned long long mend)
> +static int crash_realloc_mem_range_guarded(struct crash_mem **mem_ranges)
>   {
>   	struct crash_mem *tmem = *mem_ranges;
>   
> @@ -566,7 +564,7 @@ static int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
>   			return -ENOMEM;
>   	}
>   
> -	return crash_exclude_mem_range(tmem, mstart, mend);
> +	return 0;
>   }
>   
>   /**
> @@ -604,18 +602,10 @@ 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_realloc_mem_range_guarded(mem_ranges);

What if max_nr_ranges - nr_ranges = 1, then no realloc will happen here. 
And in
elf_header_exclude_ranges we may not enough space to store additional 
memory ranges needed while excluding one or more CMA 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/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
> index dd9d92a96517..fec3622a13c9 100644
> --- a/arch/riscv/kernel/machine_kexec_file.c
> +++ b/arch/riscv/kernel/machine_kexec_file.c
> @@ -74,10 +74,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
>   	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);
> +	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
>   
>   out:
>   	kfree(cmem);
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 335fd2ee9766..d8341a48f6b3 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -186,41 +186,6 @@ static struct crash_mem *fill_up_crash_elf_data(void)
>   	return cmem;
>   }
>   
> -/*
> - * 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 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;
> -}
> -
>   static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>   {
>   	struct crash_mem *cmem = arg;
> @@ -247,8 +212,8 @@ static int prepare_elf_headers(void **addr, unsigned long *sz,
>   	if (ret)
>   		goto out;
>   
> -	/* Exclude unwanted mem ranges */
> -	ret = elf_header_exclude_ranges(cmem);
> +	/* Exclude the low 1M because it is always reserved */
> +	ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
>   	if (ret)
>   		goto out;
>   
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 99dac1aa972a..5c0de111ddc3 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -18,6 +18,7 @@
>   #include <linux/memblock.h>
>   #include <linux/kmemleak.h>
>   #include <linux/crash_core.h>
> +#include <linux/crash_reserve.h>
>   #include <linux/reboot.h>
>   #include <linux/btf.h>
>   #include <linux/objtool.h>
> @@ -161,8 +162,30 @@ static inline resource_size_t crash_resource_size(const struct resource *res)
>   	return !res->end ? 0 : resource_size(res);
>   }
>   
> +static int crash_exclude_mem_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 ret;
> +}
>   
>   int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>   			  void **addr, unsigned long *sz)
> @@ -174,6 +197,11 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>   	unsigned int cpu, i;
>   	unsigned long long notes_addr;
>   	unsigned long mstart, mend;
> +	int ret;
> +
> +	ret = crash_exclude_mem_ranges(mem);

I think the assumption here is that mem should have enough space
to hold the extra ranges created while excluding crash memory ranges.
Right now, this is not happening on powerpc for the case I mentioned
in the above comment.

Also, if crashk_cma_cnt changes in the future, or if a new type of
crash memory is added, then every architecture would need to adjust
the mem allocation accordingly. Instead, could we handle this in
generic code rather than in architecture-specific code, so that we
always ensure mem has enough space?

> +	if (ret)
> +		return ret;
>   
>   	/* extra phdr for vmcoreinfo ELF note */
>   	nr_phdr = nr_cpus + 1;

Re: [PATCH v3 1/3] crash: Exclude crash kernel memory in crash core

[Jinjie Ruan]

On 2026/2/4 20:32, Sourabh Jain wrote:
> 
> 
> On 04/02/26 15:07, Jinjie Ruan wrote:
>> The exclude of crashk_res, crashk_low_res and crashk_cma memory
>> are almost identical across different architectures, so handling them
>> in the crash core would eliminate a lot of duplication, so do
>> them in the common code.
>>
>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
>> ---
>>   arch/arm64/kernel/machine_kexec_file.c     | 12 -------
>>   arch/loongarch/kernel/machine_kexec_file.c | 12 -------
>>   arch/powerpc/kexec/ranges.c                | 16 ++-------
>>   arch/riscv/kernel/machine_kexec_file.c     |  5 +--
>>   arch/x86/kernel/crash.c                    | 39 ++--------------------
>>   kernel/crash_core.c                        | 28 ++++++++++++++++
>>   6 files changed, 34 insertions(+), 78 deletions(-)
>>

[...]

>> -static int crash_exclude_mem_range_guarded(struct crash_mem
>> **mem_ranges,
>> -                       unsigned long long mstart,
>> -                       unsigned long long mend)
>> +static int crash_realloc_mem_range_guarded(struct crash_mem
>> **mem_ranges)
>>   {
>>       struct crash_mem *tmem = *mem_ranges;
>>   @@ -566,7 +564,7 @@ static int
>> crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
>>               return -ENOMEM;
>>       }
>>   -    return crash_exclude_mem_range(tmem, mstart, mend);
>> +    return 0;
>>   }
>>     /**
>> @@ -604,18 +602,10 @@ 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_realloc_mem_range_guarded(mem_ranges);
> 
> What if max_nr_ranges - nr_ranges = 1, then no realloc will happen here.
> And in
> elf_header_exclude_ranges we may not enough space to store additional
> memory ranges needed while excluding one or more CMA ranges.

You're absolutely right — if max_nr_ranges - nr_ranges == 1 we skip the
realloc, yet elf_header_exclude_ranges() can easily need more than one
extra slot.

Thanks for catching this.
Jinjie

> 
>>       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

[...]

>>   +static int crash_exclude_mem_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 ret;
>> +}
>>     int crash_prepare_elf64_headers(struct crash_mem *mem, int
>> need_kernel_map,
>>                 void **addr, unsigned long *sz)
>> @@ -174,6 +197,11 @@ int crash_prepare_elf64_headers(struct crash_mem
>> *mem, int need_kernel_map,
>>       unsigned int cpu, i;
>>       unsigned long long notes_addr;
>>       unsigned long mstart, mend;
>> +    int ret;
>> +
>> +    ret = crash_exclude_mem_ranges(mem);
> 
> I think the assumption here is that mem should have enough space
> to hold the extra ranges created while excluding crash memory ranges.
> Right now, this is not happening on powerpc for the case I mentioned
> in the above comment.

Yes, as you mentioned above.

> 
> Also, if crashk_cma_cnt changes in the future, or if a new type of
> crash memory is added, then every architecture would need to adjust
> the mem allocation accordingly. Instead, could we handle this in
> generic code rather than in architecture-specific code, so that we
> always ensure mem has enough space?

I agree — hard-coding the worst-case count in every arch is a
maintenance trap.
Let's move the size calculation (and the realloc if needed) into the
generic crash core so that:

- New CMA regions or future crash-memory types are automatically
accounted for;

- Each architecture no longer has to play whack-a-mole with its private
array size.

Thanks for the suggestion.

> 
>> +    if (ret)
>> +        return ret;
>>         /* extra phdr for vmcoreinfo ELF note */
>>       nr_phdr = nr_cpus + 1;
>