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

[Sourabh Jain]

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 <adityag at linux.ibm.com>
Cc: Alexander Graf <graf at amazon.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Baoquan He <baoquan.he at linux.dev>
Cc: Christophe Leroy (CS GROUP) <chleroy at kernel.org>
Cc: Hari Bathini <hbathini at linux.ibm.com>
Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Mike Rapoport <rppt at kernel.org>
Cc: Nicholas Piggin <npiggin at gmail.com>
Cc: Pasha Tatashin <pasha.tatashin at soleen.com>
Cc: Pratyush Yadav <pratyush at kernel.org>
Cc: Ritesh Harjani (IBM) <ritesh.list at gmail.com>
Cc: Shivang Upadhyay <shivangu at linux.ibm.com>
Cc: Shrikanth Hegde <sshegde at linux.ibm.com>
Cc: kexec at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
---
 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