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

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Date:	Thu, 30 Jun 2016 17:12:15 -0700
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	x86@...nel.org, linux-mm@...ck.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, bp@...en8.de, ak@...ux.intel.com,
	mhocko@...e.com, Dave Hansen <dave@...1.net>,
	dave.hansen@...ux.intel.com, minchan@...nel.org
Subject: [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);
 
 			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:
_