linux-kernel - [18/24] x86, AMD: Fix ARAT feature setting again

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Message-Id: <20110519183127.411610091@clark.kroah.org>
Date:	Thu, 19 May 2011 11:30:50 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Boris Ostrovsky <Boris.Ostrovsky@....com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Greg Kroah-Hartman <greg@...ah.com>,
	Hans Rosenfeld <hans.rosenfeld@....com>,
	Nick Bowler <nbowler@...iptictech.com>,
	Joerg-Volker-Peetz <jvpeetz@....de>,
	Borislav Petkov <borislav.petkov@....com>,
	Ingo Molnar <mingo@...e.hu>
Subject: [18/24] x86, AMD: Fix ARAT feature setting again

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------
Content-Length: 1475
Lines: 39

From: Borislav Petkov <borislav.petkov@....com>

commit 14fb57dccb6e1defe9f89a66f548fcb24c374c1d upstream.

Trying to enable the local APIC timer on early K8 revisions
uncovers a number of other issues with it, in conjunction with
the C1E enter path on AMD. Fixing those causes much more churn
and troubles than the benefit of using that timer brings so
don't enable it on K8 at all, falling back to the original
functionality the kernel had wrt to that.

Reported-and-bisected-by: Nick Bowler <nbowler@...iptictech.com>
Cc: Boris Ostrovsky <Boris.Ostrovsky@....com>
Cc: Andreas Herrmann <andreas.herrmann3@....com>
Cc: Greg Kroah-Hartman <greg@...ah.com>
Cc: Hans Rosenfeld <hans.rosenfeld@....com>
Cc: Nick Bowler <nbowler@...iptictech.com>
Cc: Joerg-Volker-Peetz <jvpeetz@....de>
Signed-off-by: Borislav Petkov <borislav.petkov@....com>
Link: http://lkml.kernel.org/r/1305636919-31165-3-git-send-email-bp@amd64.org
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kernel/cpu/amd.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -566,7 +566,7 @@ static void __cpuinit init_amd(struct cp
 #endif
 
 	/* As a rule processors have APIC timer running in deep C states */
-	if (c->x86 >= 0xf && !cpu_has_amd_erratum(amd_erratum_400))
+	if (c->x86 > 0xf && !cpu_has_amd_erratum(amd_erratum_400))
 		set_cpu_cap(c, X86_FEATURE_ARAT);
 
 	/*


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