On 10/11/25 12:38, Baoquan he wrote:
On 11/10/25 at 10:01am, Sourabh Jain wrote:
Add a sysfs entry /sys/kernel/kexec/crash_cma_ranges to expose all
CMA crashkernel ranges.
I am not against this way. While wondering if it's more appropriate to
export them into iomem_resource just like crashk_res and crashk_low_res
doing.
Handling conflict is challenging. Hence we don't export crashk_res and
crashk_low_res to iomem on powerpc. Checkout [1]
And I think conflicts can occur regardless of the order in which System
RAM and
Crash CMA ranges are added to iomem.
[1]
https://lore.kernel.org/all/[email protected]/
- Sourabh Jain
This allows userspace tools configuring kdump to determine how much
memory is reserved for crashkernel. If CMA is used, tools can warn
users when attempting to capture user pages with CMA reservation.
The new sysfs hold the CMA ranges in below format:
cat /sys/kernel/kexec/crash_cma_ranges
100000000-10c7fffff
Cc: Aditya Gupta <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Baoquan he <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Hari Bathini <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Mahesh J Salgaonkar <[email protected]>
Cc: Pingfan Liu <[email protected]>
Cc: Ritesh Harjani (IBM) <[email protected]>
Cc: Shivang Upadhyay <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Sourabh Jain <[email protected]>
---
Changelog:
- Add the missing hunk to export crash_cma_ranges sysfs
---
.../ABI/testing/sysfs-kernel-kexec-kdump | 10 ++++++++++
kernel/kexec_core.c | 17 +++++++++++++++++
2 files changed, 27 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
index 00c00f380fea..f59051b5d96d 100644
--- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
+++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
@@ -49,3 +49,13 @@ Description: read only
is used by the user space utility kexec to support updating the
in-kernel kdump image during hotplug operations.
User: Kexec tools
+
+What: /sys/kernel/kexec/crash_cma_ranges
+Date: Nov 2025
+Contact: [email protected]
+Description: read only
+ Provides information about the memory ranges reserved from
+ the Contiguous Memory Allocator (CMA) area that are allocated
+ to the crash (kdump) kernel. It lists the start and end physical
+ addresses of CMA regions assigned for crashkernel use.
+User: kdump service
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 7476a46de5d6..da6ff72b4669 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1271,6 +1271,22 @@ static ssize_t crash_size_store(struct kobject *kobj,
}
static struct kobj_attribute crash_size_attr = __ATTR_RW(crash_size);
+static ssize_t crash_cma_ranges_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+
+ ssize_t len = 0;
+ int i;
+
+ for (i = 0; i < crashk_cma_cnt; ++i) {
+ len += sysfs_emit_at(buf, len, "%08llx-%08llx\n",
+ crashk_cma_ranges[i].start,
+ crashk_cma_ranges[i].end);
+ }
+ return len;
+}
+static struct kobj_attribute crash_cma_ranges_attr =
__ATTR_RO(crash_cma_ranges);
+
#ifdef CONFIG_CRASH_HOTPLUG
static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
@@ -1289,6 +1305,7 @@ static struct attribute *kexec_attrs[] = {
#ifdef CONFIG_CRASH_DUMP
&crash_loaded_attr.attr,
&crash_size_attr.attr,
+ &crash_cma_ranges_attr.attr,
#ifdef CONFIG_CRASH_HOTPLUG
&crash_elfcorehdr_size_attr.attr,
#endif
--
2.51.1
