[RFC PATCH 3/3] powerpc/kho: exclude THP and HUGETLB_PAGE

Enabling CONFIG_KEXEC_HANDOVER together with CONFIG_TRANSPARENT_HUGEPAGE
or CONFIG_HUGETLB_PAGE on powerpc fails to build:

    kernel/liveupdate/kexec_handover.c:49:39: error: expression in static assertion is not constant
       49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES);
    ./include/linux/build_bug.h:80:56: note: in definition of macro '__static_assert'
       80 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
          |                                                        ^~~~
    kernel/liveupdate/kexec_handover.c:49:1: note: in expansion of macro 'static_assert'
       49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES);

CMA_MIN_ALIGNMENT_BYTES is derived from pageblock_order, which on
powerpc is not a compile-time constant when THP or HUGETLB_PAGE is
enabled -- powerpc can determine huge page size at runtime in that
configuration, so pageblock_order becomes a variable rather than a
constant expression. KHO's static_assert() on
SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES then fails to
compile, since it requires both sides to be constant expressions.

Until CMA_MIN_ALIGNMENT_BYTES (or KHO's use of it) is made to handle
the non-constant pageblock_order case on powerpc, exclude
TRANSPARENT_HUGEPAGE and HUGETLB_PAGE from ARCH_SUPPORTS_KEXEC_HANDOVER
so the two can't be enabled together and hit this build failure.

Cc: Aditya Gupta <[email protected]>
Cc: Alexander Graf <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Christophe Leroy (CS GROUP) <[email protected]>
Cc: Hari Bathini <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Mahesh Salgaonkar <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Pasha Tatashin <[email protected]>
Cc: Pratyush Yadav <[email protected]>
Cc: Ritesh Harjani (IBM) <[email protected]>
Cc: Shivang Upadhyay <[email protected]>
Cc: Shrikanth Hegde <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Sourabh Jain <[email protected]>
---
 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 61350d3e7a19..f68b9fc883ba 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -720,6 +720,7 @@ config ARCH_SUPPORTS_KEXEC_HANDOVER
 	def_bool y
 	depends on PPC64
 	depends on !CRASH_DUMP
+	depends on !TRANSPARENT_HUGEPAGE && !HUGETLB_PAGE
 
 config ARCH_SUPPORTS_CRASH_HOTPLUG
 	def_bool y
-- 
2.55.0