linux-kernel - Re: [PATCH 4/6] mm: move flush in madvise_free_pte

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Date:	Fri, 01 Jul 2016 16:30:23 +0800
From:	"Hillf Danton" <hillf.zj@...baba-inc.com>
To:	"'Dave Hansen'" <dave@...1.net>,
	"Dave Hansen" <dave.hansen@...ux.intel.com>
Cc:	"Minchan Kim" <minchan@...nel.org>,
	"linux-kernel" <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH 4/6] mm: move flush in madvise_free_pte_range()

> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> I think this code is OK and does not *need* to be patched.  We
> are just rewriting the PTE without the Accessed and Dirty bits.
> The hardware could come along and set them at any time with or
> without the erratum that this series addresses
> 
> But this does make the ptep_get_and_clear_full() and
> tlb_remove_tlb_entry() calls here more consistent with the other
> places they are used together and look *obviously* the same
> between call-sites.
> 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Minchan Kim <minchan@...nel.org>
> ---
> 
>  b/mm/madvise.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff -puN mm/madvise.c~knl-leak-40-madvise_free_pte_range-move-flush mm/madvise.c
> --- a/mm/madvise.c~knl-leak-40-madvise_free_pte_range-move-flush	2016-06-30 17:10:42.557246755 -0700
> +++ b/mm/madvise.c	2016-06-30 17:10:42.561246936 -0700
> @@ -369,13 +369,13 @@ static int madvise_free_pte_range(pmd_t
>  			 */
>  			ptent = ptep_get_and_clear_full(mm, addr, pte,
>  							tlb->fullmm);
> +			tlb_remove_tlb_entry(tlb, pte, addr);
> 

Then the current comment has to be updated, no?-/

thanks
Hillf
>  			ptent = pte_mkold(ptent);
>  			ptent = pte_mkclean(ptent);
>  			set_pte_at(mm, addr, pte, ptent);
>  			if (PageActive(page))
>  				deactivate_page(page);
> -			tlb_remove_tlb_entry(tlb, pte, addr);
>  		}
>  	}
>  out:
> _
>