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Date:   Wed, 10 Mar 2021 11:33:47 +1000
From:   Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v2 36/43] powerpc/32: Set current->thread.regs in C
 interrupt entry
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Paul Mackerras <paulus@samba.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <cover.1615291471.git.christophe.leroy@csgroup.eu>
        <8d523f9ecee1de0515cc31d43030c12ab171a670.1615291474.git.christophe.leroy@csgroup.eu>
In-Reply-To: <8d523f9ecee1de0515cc31d43030c12ab171a670.1615291474.git.christophe.leroy@csgroup.eu>
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Excerpts from Christophe Leroy's message of March 9, 2021 10:10 pm:
> No need to do that is assembly, do it in C.

Hmm. No issues with the patch as such, but why does ppc32 need this but=20
not 64? AFAIKS 64 sets this when a thread is created.

Thanks,
Nick

>=20
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/interrupt.h | 4 +++-
>  arch/powerpc/kernel/entry_32.S       | 3 +--
>  2 files changed, 4 insertions(+), 3 deletions(-)
>=20
> diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/=
asm/interrupt.h
> index 861e6eadc98c..e6d71c2e3aa2 100644
> --- a/arch/powerpc/include/asm/interrupt.h
> +++ b/arch/powerpc/include/asm/interrupt.h
> @@ -33,8 +33,10 @@ static inline void interrupt_enter_prepare(struct pt_r=
egs *regs, struct interrup
>  	if (!arch_irq_disabled_regs(regs))
>  		trace_hardirqs_off();
> =20
> -	if (user_mode(regs))
> +	if (user_mode(regs)) {
> +		current->thread.regs =3D regs;
>  		account_cpu_user_entry();
> +	}
>  #endif
>  	/*
>  	 * Book3E reconciles irq soft mask in asm
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_3=
2.S
> index 8fe1c3fdfa6e..815a4ff1ba76 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -52,8 +52,7 @@
>  prepare_transfer_to_handler:
>  	andi.	r0,r9,MSR_PR
>  	addi	r12, r2, THREAD
> -	beq	2f			/* if from user, fix up THREAD.regs */
> -	stw	r3,PT_REGS(r12)
> +	beq	2f
>  #ifdef CONFIG_PPC_BOOK3S_32
>  	kuep_lock r11, r12
>  #endif
> --=20
> 2.25.0
>=20
>=20