linux-kernel - Re: [PATCH 11/18] ARC: mm: move MMU specific bits out of entry code

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Message-ID: <YRO/VSMNi00X37xQ@kernel.org>
Date:   Wed, 11 Aug 2021 15:15:17 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Vineet Gupta <vgupta@...nel.org>
Cc:     linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH 11/18] ARC: mm: move MMU specific bits out of entry code

I believe a few words here would be useful even for the future version of
yourself ;-)

On Tue, Aug 10, 2021 at 05:42:51PM -0700, Vineet Gupta wrote:
> Signed-off-by: Vineet Gupta <vgupta@...nel.org>
> ---
>  arch/arc/kernel/entry.S | 6 ------
>  arch/arc/mm/tlb.c       | 3 +++
>  2 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
> index 2cb8dfe866b6..684efd094520 100644
> --- a/arch/arc/kernel/entry.S
> +++ b/arch/arc/kernel/entry.S
> @@ -101,12 +101,6 @@ ENTRY(EV_MachineCheck)
>  	lr  r0, [efa]
>  	mov r1, sp
>  
> -	; hardware auto-disables MMU, re-enable it to allow kernel vaddr
> -	; access for say stack unwinding of modules for crash dumps
> -	lr	r3, [ARC_REG_PID]
> -	or	r3, r3, MMU_ENABLE
> -	sr	r3, [ARC_REG_PID]
> -
>  	lsr  	r3, r2, 8
>  	bmsk 	r3, r3, 7
>  	brne    r3, ECR_C_MCHK_DUP_TLB, 1f
> diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
> index b68d5798327b..34f16e0b41e6 100644
> --- a/arch/arc/mm/tlb.c
> +++ b/arch/arc/mm/tlb.c
> @@ -813,5 +813,8 @@ void do_tlb_overlap_fault(unsigned long cause, unsigned long address,
>  		}
>  	}
>  
> +	/* Re-enable MMU as hardware may have auto-disabled it upon exception */
> +	write_aux_reg(ARC_REG_PID, read_aux_reg(ARC_REG_PID) | MMU_ENABLE);
> +
>  	local_irq_restore(flags);
>  }
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.