linux-kernel - Re: [PATCH] powerpc/32: Remove redundant test in transfer_to

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Message-ID: <8a7bb4c6-6366-cb0d-5c9f-4f1809b9a3a3@c-s.fr>
Date:   Tue, 18 Apr 2017 13:27:50 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/32: Remove redundant test in
 transfer_to_handler()



Le 14/04/2017 à 15:31, Christophe Leroy a écrit :
> As stated in the comment on top of transfer_to_handler(),
> all callers set cr0.eq if the exception occurred in kernel mode
> (i.e. MSR:PR = 0)
>
> Therefore, it is not needed to do the test again

Indeed, all callers set cr0.eq as required .... except that some of
them just destroy it by inserting another test before calling 
transfer_to_handler().

So this patch cannot be applied as is at the time being.

Christophe

>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>  arch/powerpc/kernel/entry_32.S | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index a38600949f3a..0651a7438fa6 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -141,7 +141,6 @@ transfer_to_handler:
>  	stw	r2,GPR2(r11)
>  	stw	r12,_NIP(r11)
>  	stw	r9,_MSR(r11)
> -	andi.	r2,r9,MSR_PR
>  	mfctr	r12
>  	mfspr	r2,SPRN_XER
>  	stw	r12,_CTR(r11)
>