[PATCH v2 3/6] crash: let arch decide crash memory export to iomem_resource

Sourabh Jain
2025-01-21T11:55:17Z

insert_crashkernel_resources() adds crash memory to iomem_resource if
generic crashkernel reservation is enabled on an architecture.

On PowerPC, system RAM is added to iomem_resource. See commit
c40dd2f766440 ("powerpc: Add System RAM to /proc/iomem").

Enabling generic crashkernel reservation on PowerPC leads to a conflict
when system RAM is added to iomem_resource because a part of the system
RAM, the crashkernel memory, has already been added to iomem_resource.

The next commit in the series "powerpc/crash: use generic crashkernel
reservation" enables generic crashkernel reservation on PowerPC. If the
crashkernel is added to iomem_resource, the kernel fails to add
system RAM to /proc/iomem and prints the following traces:

CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc2+
snip...
NIP [c000000002016b3c] add_system_ram_resources+0xf0/0x15c
LR [c000000002016b34] add_system_ram_resources+0xe8/0x15c
Call Trace:
[c00000000484bbc0] [c000000002016b34] add_system_ram_resources+0xe8/0x15c
[c00000000484bc20] [c000000000010a4c] do_one_initcall+0x7c/0x39c
[c00000000484bd00] [c000000002005418] do_initcalls+0x144/0x18c
[c00000000484bd90] [c000000002005714] kernel_init_freeable+0x21c/0x290
[c00000000484bdf0] [c0000000000110f4] kernel_init+0x2c/0x1b8
[c00000000484be50] [c00000000000dd3c] ret_from_kernel_user_thread+0x14/0x1c

To avoid this, an architecture hook is added in
insert_crashkernel_resources(), allowing the architecture to decide
whether crashkernel memory should be added to iomem_resource.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan he <bhe@redhat.com>
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: kexec@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
include/linux/crash_reserve.h | 11 +++++++++++
kernel/crash_reserve.c | 3 +++
2 files changed, 14 insertions(+)

diff --git a/include/linux/crash_reserve.h b/include/linux/crash_reserve.h
index 1fe7e7d1b214..f1205d044dae 100644
--- a/include/linux/crash_reserve.h
+++ b/include/linux/crash_reserve.h
@@ -18,6 +18,17 @@ int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base,
unsigned long long *low_size, bool *high);

+#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
+
+#ifndef arch_add_crash_res_to_iomem
+static inline bool arch_add_crash_res_to_iomem(void)
+{
+ return true;
+}
+#endif
+
+#endif
+
#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
#ifndef DEFAULT_CRASH_KERNEL_LOW_SIZE
#define DEFAULT_CRASH_KERNEL_LOW_SIZE (128UL << 20)
diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
index aff7c0fdbefa..190104f32fe1 100644
--- a/kernel/crash_reserve.c
+++ b/kernel/crash_reserve.c
@@ -460,6 +460,9 @@ void __init reserve_crashkernel_generic(unsigned long long crash_size,
#ifndef HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
static __init int insert_crashkernel_resources(void)
{
+ if (!arch_add_crash_res_to_iomem())
+ return 0;
+
if (crashk_res.start < crashk_res.end)
insert_resource(&iomem_resource, &crashk_res);

--
2.47.1