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

[Christophe Leroy]

Le 10/03/2021 à 02:29, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of March 9, 2021 10:09 pm:
> > 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
>
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   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