[PATCH] powerpc/tlb: Implement book3s/32/tlbflush.h local_flush_tlb_page_psize

[Benjamin Gray]

The commit introducing this function implemented it as a build bug on this
platform to make the compiler happy, as the only use in the code is guarded
behind a radix_enabled() conditional.

GCC recognises that cpu_has_feature(MMU_FTR_TYPE_RADIX) returns false on this
platform and eliminates the build bug as dead code. However, when
CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is enabled, the assertion and possible
call to early_cpu_... prevents Clang from eliminating any code that's
conditional on the return value. So Clang triggers the build bug as reported
by the kernel test robot:

https://lore.kernel.org/llvm/202301212348.eDkowvfF-lkp@intel.com

Fixes: 274d842fa1ef ("powerpc/tlb: Add local flush for page given mm_struct and psize")
Reported-by: kernel test robot <lkp at intel.com>
Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>
---

Supersedes https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20230124215424.9068-1-bgray@linux.ibm.com/

---
 arch/powerpc/include/asm/book3s/32/tlbflush.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/tlbflush.h b/arch/powerpc/include/asm/book3s/32/tlbflush.h
index 4be572908124..cde3b6f5d563 100644
--- a/arch/powerpc/include/asm/book3s/32/tlbflush.h
+++ b/arch/powerpc/include/asm/book3s/32/tlbflush.h
@@ -2,8 +2,6 @@
 #ifndef _ASM_POWERPC_BOOK3S_32_TLBFLUSH_H
 #define _ASM_POWERPC_BOOK3S_32_TLBFLUSH_H

-#include <linux/build_bug.h>
-
 #define MMU_NO_CONTEXT      (0)
 /*
  * TLB flushing for "classic" hash-MMU 32-bit CPUs, 6xx, 7xx, 7xxx
@@ -80,7 +78,7 @@ static inline void local_flush_tlb_page(struct vm_area_struct *vma,
 static inline void local_flush_tlb_page_psize(struct mm_struct *mm,
 					      unsigned long vmaddr, int psize)
 {
-	BUILD_BUG();
+	flush_range(mm, vmaddr, vmaddr + PAGE_SIZE);
 }

 static inline void local_flush_tlb_mm(struct mm_struct *mm)

base-commit: ca272751ba18ca8f137af631cbc9f3f987fab6e3
--
2.39.1