kho: mm: don't allow deferred struct page with KHO

KHO uses struct pages for the preserved memory early in boot, however,
with deferred struct page initialization, only a small portion of memory
has properly initialized struct pages.

This problem was detected where vmemmap is poisoned, and illegal flag
combinations are detected.

Don't allow them to be enabled together, and later we will have to teach
KHO to work properly with deferred struct page init kernel feature.

Link: https://lkml.kernel.org/r/20250808201804.772010-3-pasha.tatashin@soleen.com
Fixes: 4e1d010 ("kexec: add config option for KHO")
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Vasilevsky <dave@vasilevsky.ca>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: soleen

kernel/Kconfig.kexec

@@ -97,6 +97,7 @@ config KEXEC_JUMP
 config KEXEC_HANDOVER
 	bool "kexec handover"
 	depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
+	depends on !DEFERRED_STRUCT_PAGE_INIT
 	select MEMBLOCK_KHO_SCRATCH
 	select KEXEC_FILE
 	select DEBUG_FS