Re: [PATCH v2 28/43] powerpc/64e: Call bad_page_fault() from do_page_fault()

Le 10/03/2021 à 02:29, Nicholas Piggin a écrit :

Excerpts from Christophe Leroy's message of March 9, 2021 10:09 pm:

quoted

book3e/64 is the last one calling __bad_page_fault()
from assembly.

Save non volatile registers before calling do_page_fault()
and modify do_page_fault() to call __bad_page_fault()
for all platforms.

Then it can be refactored by the call of bad_page_fault()
which avoids the duplication of the exception table search.

This can go in with the 64e change after your series. I think it should
be ready for the next merge window as well.

Yes, I thought it would pull more optimisation, but at the end it doesn't bring anythink, so I'll 
drop it for now and leave it to you for your series.

Thanks,
Nick

quoted

Signed-off-by: Christophe Leroy <redacted>
---
  arch/powerpc/kernel/exceptions-64e.S |  8 +-------
  arch/powerpc/mm/fault.c              | 17 ++++-------------
  2 files changed, 5 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index e8eb9992a270..b60f89078a3f 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S

@@ -1010,15 +1010,9 @@ storage_fault_common:
  	addi	r3,r1,STACK_FRAME_OVERHEAD
  	ld	r14,PACA_EXGEN+EX_R14(r13)
  	ld	r15,PACA_EXGEN+EX_R15(r13)
+	bl	save_nvgprs
  	bl	do_page_fault
-	cmpdi	r3,0
-	bne-	1f
  	b	ret_from_except_lite
-1:	bl	save_nvgprs
-	mr	r4,r3
-	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	__bad_page_fault
-	b	ret_from_except
  
  /*
   * Alignment exception doesn't fit entirely in the 0x100 bytes so it

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 2e54bac99a22..7bcff3fca110 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c

@@ -541,24 +541,15 @@ NOKPROBE_SYMBOL(___do_page_fault);
  
  static long __do_page_fault(struct pt_regs *regs)
  {
-	const struct exception_table_entry *entry;
  	long err;
  
  	err = ___do_page_fault(regs, regs->dar, regs->dsisr);
  	if (likely(!err))
-		return err;
-
-	entry = search_exception_tables(regs->nip);
-	if (likely(entry)) {
-		instruction_pointer_set(regs, extable_fixup(entry));
  		return 0;
-	} else if (!IS_ENABLED(CONFIG_PPC_BOOK3E_64)) {
-		__bad_page_fault(regs, err);
-		return 0;
-	} else {
-		/* 32 and 64e handle the bad page fault in asm */
-		return err;
-	}
+
+	bad_page_fault(regs, err);
+
+	return 0;
  }
  NOKPROBE_SYMBOL(__do_page_fault);
  

-- 
2.25.0