Re: tlb_batch_add_one()

[Nitin Gupta <nitin.m.gupta@oracle.com>]

On 3/30/17 2:54 PM, David Miller wrote:
> From: David Miller <davem@davemloft.net>
> Date: Thu, 30 Mar 2017 14:25:53 -0700 (PDT)
> 
>> From: Nitin Gupta <nitin.m.gupta@oracle.com>
>> Date: Thu, 30 Mar 2017 13:47:11 -0700
>>
>>> I will be sending a fix for these call-sites today.
>>
>> I already have a fix I'm testing now which I'll check in after my
>> regression test passes.
> 
> So even with the shifts fixed, as per the patch below, I'm still getting
> corruptions during gcc bootstraps.
> 
> If I cannot figure out what the problem is by the end of the day I'm
> reverting the change.  I've already spend a week trying to figure out
> what introduced these regressions...
> 
> diff --git a/arch/sparc/mm/tlb.c b/arch/sparc/mm/tlb.c
> index afda3bb..ee8066c 100644
> --- a/arch/sparc/mm/tlb.c
> +++ b/arch/sparc/mm/tlb.c
> @@ -154,7 +154,7 @@ static void tlb_batch_pmd_scan(struct mm_struct *mm, unsigned long vaddr,
>  		if (pte_val(*pte) & _PAGE_VALID) {
>  			bool exec = pte_exec(*pte);
>  
> -			tlb_batch_add_one(mm, vaddr, exec, false);
> +			tlb_batch_add_one(mm, vaddr, exec, PAGE_SHIFT);
>  		}
>  		pte++;
>  		vaddr += PAGE_SIZE;
> @@ -209,9 +209,9 @@ void set_pmd_at(struct mm_struct *mm, unsigned long addr,
>  			pte_t orig_pte = __pte(pmd_val(orig));
>  			bool exec = pte_exec(orig_pte);
>  
> -			tlb_batch_add_one(mm, addr, exec, true);
> +			tlb_batch_add_one(mm, addr, exec, REAL_HPAGE_SHIFT);
>  			tlb_batch_add_one(mm, addr + REAL_HPAGE_SIZE, exec,
> -					true);
> +					  REAL_HPAGE_SHIFT);


Shifts are still wrong: tlb_batch_add_one -> flush_tsb_user_page expects
HPAGE_SHIFT to be passed for 8M pages so that 'HUGE' tsb is flushed
instead of the BASE one. So, we need to pass HPAGE_SHIFT here.

Also, I see that sun4v_tte_to_shift() should return HPAGE_SHIFT for 4MB
case instead of REAL_HPAGE_SHIFT (same for sun4u version).

And finally, huge_tte_to_shift() can have the size check removed after
fixing huge_tte_to_shift() as above.

Currently my test machine is having some disk issues, so I will be back
with results once the machine is back up.

Nitin


>  		} else {
>  			tlb_batch_pmd_scan(mm, addr, orig);
>  		}
> --
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