This is a note to let you know that I've just added the patch titled
x86, AMD: Set ARAT feature on AMD processors
to the 2.6.38-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-amd-set-arat-feature-on-amd-processors.patch
and it can be found in the queue-2.6.38 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From b87cf80af3ba4b4c008b4face3c68d604e1715c6 Mon Sep 17 00:00:00 2001
From: Boris Ostrovsky <[email protected]>
Date: Tue, 15 Mar 2011 12:13:44 -0400
Subject: x86, AMD: Set ARAT feature on AMD processors
From: Boris Ostrovsky <[email protected]>
commit b87cf80af3ba4b4c008b4face3c68d604e1715c6 upstream.
Support for Always Running APIC timer (ARAT) was introduced in
commit db954b5898dd3ef3ef93f4144158ea8f97deb058. This feature
allows us to avoid switching timers from LAPIC to something else
(e.g. HPET) and go into timer broadcasts when entering deep
C-states.
AMD processors don't provide a CPUID bit for that feature but
they also keep APIC timers running in deep C-states (except for
cases when the processor is affected by erratum 400). Therefore
we should set ARAT feature bit on AMD CPUs.
Tested-by: Borislav Petkov <[email protected]>
Acked-by: Andreas Herrmann <[email protected]>
Acked-by: Mark Langsdorf <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kernel/cpu/amd.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -594,6 +594,10 @@ 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))
+ set_cpu_cap(c, X86_FEATURE_ARAT);
}
#ifdef CONFIG_X86_32
Patches currently in stable-queue which might be from [email protected]
are
queue-2.6.38/x86-amd-set-arat-feature-on-amd-processors.patch
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