kdump: defer the insertion of crashkernel resources

In /proc/iomem, sub-regions should be inserted after their parent,
otherwise the insertion of parent resource fails.  But after generic
crashkernel reservation applied, in both RISC-V and ARM64 (LoongArch will
also use generic reservation later on), crashkernel resources are inserted
before their parent, which causes the parent disappear in /proc/iomem.  So
we defer the insertion of crashkernel resources to an early_initcall().

1, Without 'crashkernel' parameter:

 100d0100-100d01ff : LOON0001:00
   100d0100-100d01ff : LOON0001:00 LOON0001:00
 100e0000-100e0bff : LOON0002:00
   100e0000-100e0bff : LOON0002:00 LOON0002:00
 1fe001e0-1fe001e7 : serial
 90400000-fa17ffff : System RAM
   f6220000-f622ffff : Reserved
   f9ee0000-f9ee3fff : Reserved
   fa120000-fa17ffff : Reserved
 fa190000-fe0bffff : System RAM
   fa190000-fa1bffff : Reserved
 fe4e0000-47fffffff : System RAM
   43c000000-441ffffff : Reserved
   47ff98000-47ffa3fff : Reserved
   47ffa4000-47ffa7fff : Reserved
   47ffa8000-47ffabfff : Reserved
   47ffac000-47ffaffff : Reserved
   47ffb0000-47ffb3fff : Reserved

2, With 'crashkernel' parameter, before this patch:

 100d0100-100d01ff : LOON0001:00
   100d0100-100d01ff : LOON0001:00 LOON0001:00
 100e0000-100e0bff : LOON0002:00
   100e0000-100e0bff : LOON0002:00 LOON0002:00
 1fe001e0-1fe001e7 : serial
 e6200000-f61fffff : Crash kernel
 fa190000-fe0bffff : System RAM
   fa190000-fa1bffff : Reserved
 fe4e0000-47fffffff : System RAM
   43c000000-441ffffff : Reserved
   47ff98000-47ffa3fff : Reserved
   47ffa4000-47ffa7fff : Reserved
   47ffa8000-47ffabfff : Reserved
   47ffac000-47ffaffff : Reserved
   47ffb0000-47ffb3fff : Reserved

3, With 'crashkernel' parameter, after this patch:

 100d0100-100d01ff : LOON0001:00
   100d0100-100d01ff : LOON0001:00 LOON0001:00
 100e0000-100e0bff : LOON0002:00
   100e0000-100e0bff : LOON0002:00 LOON0002:00
 1fe001e0-1fe001e7 : serial
 90400000-fa17ffff : System RAM
   e6200000-f61fffff : Crash kernel
   f6220000-f622ffff : Reserved
   f9ee0000-f9ee3fff : Reserved
   fa120000-fa17ffff : Reserved
 fa190000-fe0bffff : System RAM
   fa190000-fa1bffff : Reserved
 fe4e0000-47fffffff : System RAM
   43c000000-441ffffff : Reserved
   47ff98000-47ffa3fff : Reserved
   47ffa4000-47ffa7fff : Reserved
   47ffa8000-47ffabfff : Reserved
   47ffac000-47ffaffff : Reserved
   47ffb0000-47ffb3fff : Reserved

Link: https://lkml.kernel.org/r/20231229080213.2622204-1-chenhuacai@loongson.cnSigned-off-by: Huacai Chen <chenhuacai@loongson.cn>
Fixes: 0ab97169 ("crash_core: add generic function to do reservation")
Cc: Baoquan He <bhe@redhat.com>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: <stable@vger.kernel.org>	[6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kernel/crash_core.c

@@ -376,7 +376,6 @@ static int __init reserve_crashkernel_low(unsigned long long low_size)
 
 	crashk_low_res.start = low_base;
 	crashk_low_res.end   = low_base + low_size - 1;
-	insert_resource(&iomem_resource, &crashk_low_res);
 #endif
 	return 0;
 }
@@ -458,8 +457,19 @@ void __init reserve_crashkernel_generic(char *cmdline,
 
 	crashk_res.start = crash_base;
 	crashk_res.end = crash_base + crash_size - 1;
-	insert_resource(&iomem_resource, &crashk_res);
 }
+
+static __init int insert_crashkernel_resources(void)
+{
+	if (crashk_res.start < crashk_res.end)
+		insert_resource(&iomem_resource, &crashk_res);
+
+	if (crashk_low_res.start < crashk_low_res.end)
+		insert_resource(&iomem_resource, &crashk_low_res);
+
+	return 0;
+}
+early_initcall(insert_crashkernel_resources);
 #endif
 
 int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,