On 11/10/25 at 02:09pm, Sourabh Jain wrote: > > > 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]/
Then I would suggest you add this reason and the link into patch log to keep a record. One day people may post patch to 'optimize' this. > > > > > > 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 > > > >
