KHO requires the scratch alignment to be at least CMA_MIN_ALIGNMENT_BYTES,
and this is currently enforced with a static_assert().
That assertion breaks the build on powerpc once CONFIG_KEXEC_HANDOVER is
enabled together with CONFIG_TRANSPARENT_HUGEPAGE or CONFIG_HUGETLB_PAGE:
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 depends on pageblock_order, which is not a
compile-time constant with certain configs, such as
CONFIG_HUGETLB_PAGE_SIZE_VARIABLE on powerpc. The next patch in this
series enables KHO on powerpc, so the alignment must be checked at
runtime instead.
Replace the static_assert() with a runtime check at the start of
kho_reserve_scratch(), before any scratch memory is reserved. If the
scratch alignment is smaller than the CMA minimum alignment, warn once
and disable KHO rather than continue with a misaligned reservation.
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]>
---
kernel/liveupdate/kexec_handover.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/kernel/liveupdate/kexec_handover.c
b/kernel/liveupdate/kexec_handover.c
index 7c4d86daf86d..dc76dd6b74da 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -39,15 +39,7 @@
#include "../kexec_internal.h"
#include "kexec_handover_internal.h"
-/*
- * This is the minimal alignment required by deferred struct page init.
- * deferred_init_memmap_chunk frees memory to the buddy allocator, which looks
- * at the neighboring pages (up to MAX_PAGE_ORDER) to merge them.
- * If KHO scratch is not aligned to that value, buddy can access uninitialized
- * struct pages, which can cause a crash.
- */
#define SCRATCH_ALIGNMENT_BYTES (PAGE_SIZE * MAX_ORDER_NR_PAGES)
-static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES);
/* The magic token for preserved pages */
#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
@@ -836,6 +828,21 @@ static void __init kho_reserve_scratch(void)
if (!kho_enable)
return;
+ /*
+ * This is the minimal alignment required by deferred struct page init.
+ * deferred_init_memmap_chunk frees memory to the buddy allocator,
which looks
+ * at the neighboring pages (up to MAX_PAGE_ORDER) to merge them.
+ * If KHO scratch is not aligned to that value, buddy can access
uninitialized
+ * struct pages, which can cause a crash.
+ */
+ if (WARN_ON_ONCE(SCRATCH_ALIGNMENT_BYTES < CMA_MIN_ALIGNMENT_BYTES)) {
+ pr_err("scratch alignment %lu < CMA minimum %lu, disabling\n",
+ (unsigned long)SCRATCH_ALIGNMENT_BYTES,
+ (unsigned long)CMA_MIN_ALIGNMENT_BYTES);
+ kho_enable = false;
+ return;
+ }
+
scratch_size_update();
/* FIXME: deal with node hot-plug/remove */
--
2.55.0
