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

[Vineet Gupta]

On 8/11/21 5:15 AM, Mike Rapoport wrote:

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


"Don't pollute common entry file with MMU versions specific bits (as new 
MMU doesn't have PID register)"


However Jose thankfully pointed me (off list) that this patch is broken 
(based on some internal emails).
Any Machine check disables MMU but we now we only re-enable for TLB 
faults related MC, so this will have to be redone.


Thx,
-Vineet

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

[Mike Rapoport]

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 
> ---
>  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
>   bmskr3, r3, 7
>   brner3, 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.

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