crash: use macro to add crashk_res into iomem early for specific arch

There are regression reports[1][2] that crashkernel region on x86_64 can't
be added into iomem tree sometime.  This causes the later failure of kdump
loading.

This happened after commit 4a693ce ("kdump: defer the insertion of
crashkernel resources") was merged.

Even though, these reported issues are proved to be related to other
component, they are just exposed after above commmit applied, I still
would like to keep crashk_res and crashk_low_res being added into iomem
early as before because the early adding has been always there on x86_64
and working very well.  For safety of kdump, Let's change it back.

Here, add a macro HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY to limit that
only ARCH defining the macro can have the early adding
crashk_res/_low_res into iomem. Then define
HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY on x86 to enable it.

Note: In reserve_crashkernel_low(), there's a remnant of crashk_low_res
handling which was mistakenly added back in commit 85fcde4 ("kexec:
split crashkernel reservation code out from crash_core.c").

[1]
[PATCH V2] x86/kexec: do not update E820 kexec table for setup_data
https://lore.kernel.org/all/[email protected]/T/#u

[2]
Question about Address Range Validation in Crash Kernel Allocation
https://lore.kernel.org/all/[email protected]/T/#u

Link: https://lkml.kernel.org/r/ZgDYemRQ2jxjLkq+@MiWiFi-R3L-srv
Fixes: 4a693ce ("kdump: defer the insertion of crashkernel resources")
Signed-off-by: Baoquan He <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: Li Huafei <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Baoquan He

arch/x86/include/asm/crash_reserve.h

@@ -39,4 +39,6 @@ static inline unsigned long crash_low_size_default(void)
 #endif
 }
 
+#define HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
+
 #endif /* _X86_CRASH_RESERVE_H */

kernel/crash_reserve.c

@@ -366,7 +366,9 @@ 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;
+#ifdef HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
 	insert_resource(&iomem_resource, &crashk_low_res);
+#endif
 #endif
 	return 0;
 }
@@ -448,8 +450,12 @@ void __init reserve_crashkernel_generic(char *cmdline,
 
 	crashk_res.start = crash_base;
 	crashk_res.end = crash_base + crash_size - 1;
+#ifdef HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
+	insert_resource(&iomem_resource, &crashk_res);
+#endif
 }
 
+#ifndef HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
 static __init int insert_crashkernel_resources(void)
 {
 	if (crashk_res.start < crashk_res.end)
@@ -462,3 +468,4 @@ static __init int insert_crashkernel_resources(void)
 }
 early_initcall(insert_crashkernel_resources);
 #endif
+#endif