linux-kernel - Re: [PATCH] Revert "x86-64, init: Do not set NX bits on non-NX capable hardware"

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Date:	Mon, 20 May 2013 20:23:06 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>, "Rafael J. Wysocki" <rjw@...k.pl>,
	the arch/x86 maintainers <x86@...nel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "x86-64, init: Do not set NX bits on non-NX
 capable hardware"

On Mon 20-05-13 10:21:09, Linus Torvalds wrote:
> On Mon, May 20, 2013 at 9:43 AM, Michal Hocko <mhocko@...e.cz> wrote:
> >
> > The configuration has been posted in the referenced thread:
> > https://lkml.org/lkml/2013/5/14/398
> 
> Hmm. That's a regular intel i5 Sandybridge CPU. Which certainly has NX.
> 
> Hmm. secondary_startup_64 isn't __initcode, is it? I think it's used
> for resuming the other CPU's too and for CPU hotplug. Yes/no?
> 
> If so early_pmd_flags shouldn't be __initdata, I think.
> 
> Michal, does it work if you don't do the revert, but just remove the
> __initdata instead?

Right you are! The following patch on top of your tree fixes the
problem. Thanks a lot. I will leave the proper changelog to somebody who
is more familiar with the area but AFAIU the real problem is that
early_pmd_flags is no longer available beacause the section is gone.

Anyway, feel free to add my 
Tested-by: Michal Hocko <mhocko@...e.cz>
and mark it for 3.9 stable tree
---
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index dab95a8..55b6761 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -34,7 +34,7 @@
 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
 extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD];
 static unsigned int __initdata next_early_pgt = 2;
-pmdval_t __initdata early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
+pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 /* Wipe all early page tables except for the kernel symbol map */
 static void __init reset_early_page_tables(void)
-- 
Michal Hocko
SUSE Labs
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