admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

crash: export crashkernel CMA reservation to userspace

Browse Source 
Add a sysfs entry /sys/kernel/kexec_crash_cma_ranges to expose all CMA
crashkernel ranges.

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

The reason for not including Crash CMA Ranges in /proc/iomem is to avoid
conflicts.  It has been observed that contiguous memory ranges are
sometimes shown as two separate System RAM entries in /proc/iomem.  If a
CMA range overlaps two System RAM ranges, adding crashk_res to /proc/iomem
can create a conflict.  Reference [1] describes one such instance on the
PowerPC architecture.

Link: https://lkml.kernel.org/r/20251118071023.1673329-1-sourabhjain@linux.ibm.com
Link: https://lore.kernel.org/all/20251016142831.144515-1-sourabhjain@linux.ibm.com/ [1]
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Aditya Gupta <adityag@linux.ibm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sourabh Jain
2025-11-18 12:40:23 +05:30
committed by Andrew Morton
parent fdd76c8d63
commit aa0145563c
2 changed files with 31 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
Documentation/ABI/testing/sysfs-kernel-kexec-kdump
View File

@@ -41,3 +41,13 @@ 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: kexec@lists.infradead.org
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

21
kernel/ksysfs.c
View File

@@ -135,6 +135,24 @@ static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(kexec_crash_loaded);
#ifdef CONFIG_CRASH_RESERVE
static ssize_t kexec_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;
}
KERNEL_ATTR_RO(kexec_crash_cma_ranges);
#endif /* CONFIG_CRASH_RESERVE */
static ssize_t kexec_crash_size_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
@@ -260,6 +278,9 @@ static struct attribute * kernel_attrs[] = {
#ifdef CONFIG_CRASH_DUMP
&kexec_crash_loaded_attr.attr,
&kexec_crash_size_attr.attr,
#ifdef CONFIG_CRASH_RESERVE
&kexec_crash_cma_ranges_attr.attr,
#endif
#endif
#endif
#ifdef CONFIG_VMCORE_INFO