[PATCH v2] powerpc/kdump: Add support for crashkernel CMA reservation

[PATCH v2] powerpc/kdump: Add support for crashkernel CMA reservation

[Sourabh Jain]

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.

Extend crashkernel CMA reservation support to powerpc.

The following changes are made to enable CMA reservation on powerpc:

- 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 in the usable memory ranges for the
  kdump kernel to use.
- Exclude the CMA-reserved ranges from the crash kernel memory to
  prevent them from being exported through /proc/vmcore

To ensure proper CMA reservation, reserve_crashkernel_cma() is called
after pageblock_order is initialized.

Cc: Jiri Bohac <jbohac@suse.cz>
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>
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---

Changelog:

v1 -> v2:
 - Fix build warnings, ensure kernel build when CONFIG_CMA is
   disabled

---
 arch/powerpc/include/asm/kexec.h   |  7 +++++++
 arch/powerpc/kernel/setup-common.c |  4 +++-
 arch/powerpc/kexec/core.c          | 13 ++++++++++++-
 arch/powerpc/kexec/ranges.c        | 16 +++++++++++++++-
 4 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 4bbf9f699aaa..c158ffbfeadb 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -51,9 +51,16 @@
 
 #ifndef __ASSEMBLER__
 #include <asm/reg.h>
+#include <linux/crash_reserve.h>
 
 typedef void (*crash_shutdown_t)(void);
 
+#ifdef CRASHKERNEL_CMA
+void kdump_cma_reserve(void);
+#else
+static inline void kdump_cma_reserve(void) { }
+#endif
+
 #ifdef CONFIG_KEXEC_CORE
 struct kimage;
 struct pt_regs;
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 68d47c53876c..c8c42b419742 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -35,6 +35,7 @@
 #include <linux/of_irq.h>
 #include <linux/hugetlb.h>
 #include <linux/pgtable.h>
+#include <asm/kexec.h>
 #include <asm/io.h>
 #include <asm/paca.h>
 #include <asm/processor.h>
@@ -995,11 +996,12 @@ void __init setup_arch(char **cmdline_p)
 	initmem_init();
 
 	/*
-	 * Reserve large chunks of memory for use by CMA for fadump, KVM and
+	 * Reserve large chunks of memory for use by CMA for kdump, fadump, KVM and
 	 * hugetlb. These must be called after initmem_init(), so that
 	 * pageblock_order is initialised.
 	 */
 	fadump_cma_init();
+	kdump_cma_reserve();
 	kvm_cma_reserve();
 	gigantic_hugetlb_cma_reserve();
 
diff --git a/arch/powerpc/kexec/core.c b/arch/powerpc/kexec/core.c
index d1a2d755381c..6e7bf8fc868d 100644
--- a/arch/powerpc/kexec/core.c
+++ b/arch/powerpc/kexec/core.c
@@ -14,6 +14,7 @@
 #include <linux/of.h>
 #include <linux/irq.h>
 #include <linux/ftrace.h>
+#include <linux/crash_reserve.h>
 
 #include <asm/kdump.h>
 #include <asm/machdep.h>
@@ -33,6 +34,8 @@ void machine_kexec_cleanup(struct kimage *image)
 {
 }
 
+unsigned long long cma_size;
+
 /*
  * Do not allocate memory (or fail in any way) in machine_kexec().
  * We are past the point of no return, committed to rebooting now.
@@ -110,7 +113,7 @@ void __init arch_reserve_crashkernel(void)
 
 	/* use common parsing */
 	ret = parse_crashkernel(boot_command_line, total_mem_sz, &crash_size,
-				&crash_base, NULL, NULL, NULL);
+				&crash_base, NULL, &cma_size, NULL);
 
 	if (ret)
 		return;
@@ -130,6 +133,14 @@ void __init arch_reserve_crashkernel(void)
 	reserve_crashkernel_generic(crash_size, crash_base, 0, false);
 }
 
+#ifdef CRASHKERNEL_CMA
+void __init kdump_cma_reserve(void)
+{
+	if (cma_size)
+		reserve_crashkernel_cma(cma_size);
+}
+#endif
+
 int __init overlaps_crashkernel(unsigned long start, unsigned long size)
 {
 	return (start + size) > crashk_res.start && start <= crashk_res.end;
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index 3702b0bdab14..dad58fc38251 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -515,7 +515,7 @@ int get_exclude_memory_ranges(struct crash_mem **mem_ranges)
  */
 int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 {
-	int ret;
+	int ret, i;
 
 	/*
 	 * Early boot failure observed on guests when low memory (first memory
@@ -528,6 +528,13 @@ int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 	if (ret)
 		goto out;
 
+	for (i = 0; i < crashk_cma_cnt; i++) {
+		ret = add_mem_range(mem_ranges, crashk_cma_ranges[i].start,
+				    crashk_cma_ranges[i].end);
+		if (ret)
+			goto out;
+	}
+
 	ret = add_rtas_mem_range(mem_ranges);
 	if (ret)
 		goto out;
@@ -595,6 +602,13 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
 	if (ret)
 		goto out;
 
+	for (i = 0; i < crashk_cma_cnt; ++i) {
+		ret = crash_exclude_mem_range(tmem, 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
-- 
2.51.0

Re: [PATCH v2] powerpc/kdump: Add support for crashkernel CMA reservation

[Jiri Bohac]

On Thu, Oct 23, 2025 at 05:44:12PM +0530, Sourabh Jain wrote:
> @@ -595,6 +602,13 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
>  	if (ret)
>  		goto out;
>  
> +	for (i = 0; i < crashk_cma_cnt; ++i) {
> +		ret = crash_exclude_mem_range(tmem, crashk_cma_ranges[i].start,
> +					      crashk_cma_ranges[i].end);
> +		if (ret)
> +			goto out;
> +	}
> +

I think the loop needs to check if tmem->nr_ranges == tmem->max_nr_ranges and
reallocate in each iteration, just like it's done when excluding the crashk_res
region above:

        /* Reallocate memory ranges if there is no space to split ranges */
        tmem = *mem_ranges;
        if (tmem && (tmem->nr_ranges == tmem->max_nr_ranges)) {
                tmem = realloc_mem_ranges(mem_ranges);
                if (!tmem)
                        goto out;
        }

        /* Exclude crashkernel region */
        ret = crash_exclude_mem_range(tmem, crashk_res.start, crashk_res.end);
        if (ret)
                goto out;



-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

Re: [PATCH v2] powerpc/kdump: Add support for crashkernel CMA reservation

[Sourabh Jain]

On 23/10/25 20:53, Jiri Bohac wrote:
> On Thu, Oct 23, 2025 at 05:44:12PM +0530, Sourabh Jain wrote:
>> @@ -595,6 +602,13 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
>>   	if (ret)
>>   		goto out;
>>   
>> +	for (i = 0; i < crashk_cma_cnt; ++i) {
>> +		ret = crash_exclude_mem_range(tmem, crashk_cma_ranges[i].start,
>> +					      crashk_cma_ranges[i].end);
>> +		if (ret)
>> +			goto out;
>> +	}
>> +
> I think the loop needs to check if tmem->nr_ranges == tmem->max_nr_ranges and
> reallocate in each iteration, just like it's done when excluding the crashk_res
> region above:

Yeah, nice catch. I thought it would get adjusted automatically, as it is
done in the add_mem_range function.

Thanks for the review. I will update the patch and send v3.

>          /* Reallocate memory ranges if there is no space to split ranges */
>          tmem = *mem_ranges;
>          if (tmem && (tmem->nr_ranges == tmem->max_nr_ranges)) {
>                  tmem = realloc_mem_ranges(mem_ranges);
>                  if (!tmem)
>                          goto out;
>          }
>
>          /* Exclude crashkernel region */
>          ret = crash_exclude_mem_range(tmem, crashk_res.start, crashk_res.end);
>          if (ret)
>                  goto out;
>
>
>