linux-kernel - [PATCH v4 RESEND 11/11] x86/mm: Fix no-change case in try_preserve_large

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Date:	Thu, 17 Sep 2015 12:24:24 -0600
From:	Toshi Kani <toshi.kani@....com>
To:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com
Cc:	akpm@...ux-foundation.org, bp@...en8.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, jgross@...e.com,
	konrad.wilk@...cle.com, elliott@....com,
	Toshi Kani <toshi.kani@....com>
Subject: [PATCH v4 RESEND 11/11] x86/mm: Fix no-change case in try_preserve_large_page()

try_preserve_large_page() checks if new_prot is the same as
old_prot.  If so, it simply sets do_split to 0, and returns
with no-operation.  However, old_prot is set as a 4KB pgprot
value while new_prot is a large page pgprot value.

Now that old_prot is initially set from p?d_pgprot() as a
large page pgprot value, fix it by not overwriting old_prot
with a 4KB pgprot value.

Signed-off-by: Toshi Kani <toshi.kani@....com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 arch/x86/mm/pageattr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index b64a451..97735f4 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -536,7 +536,7 @@ try_preserve_large_page(pte_t *kpte, unsigned long address,
 	 * up accordingly.
 	 */
 	old_pte = *kpte;
-	old_prot = req_prot = pgprot_large_2_4k(old_prot);
+	req_prot = pgprot_large_2_4k(old_prot);
 
 	pgprot_val(req_prot) &= ~pgprot_val(cpa->mask_clr);
 	pgprot_val(req_prot) |= pgprot_val(cpa->mask_set);
--
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