From: Luming Yu <luyu@redhat.com>
Date: Mon, 30 Mar 2009 12:59:38 +0800
Subject: [x86] NONSTOP_TSC in tsc clocksource
Message-id: 49D051BA.5060503@redhat.com
O-Subject: [RHEL 5.4 PATCH] bz 474091 use NONSTOP_TSC in i386 tsc clocksource
Bugzilla: 474091
RH-Acked-by: Jiri Pirko <jpirko@redhat.com>
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>
RH-Acked-by: Peter Martuccelli <peterm@redhat.com>
RH-Acked-by: Brian Maly <bmaly@redhat.com>

Description of problem:

RH QA captured the problem when testing the NONSTOP_TSC feature with
32-bit kernel. She found the clock source under sys fs is still HPET on
hp-xw8800-01.rhts.bos.redhat.com.

Part of code got neglected from my original back port, because it
doesn't appear in the corresponding Upstream commit.

And upstream still use this:
    if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
        return 0;

The attached patch fixes the problem.

Testing status:
Successfully tested the patch with 32-bit kernel on
hp-xw8800-01.rhts.bos.redhat.com.

Brew:
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1743217

Please review and Ack

Thanks,
Luming

diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 839aba6..87c757c 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -451,9 +451,8 @@ out:
  */
 static __init int unsynchronized_tsc(void)
 {
-	/* AMD systems with constant TSCs have synchronized clocks */
-	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) &&
-	    (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)))
+	/* AMD and Intel systems with constant TSCs have synchronized clocks */
+	if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 		return 0;
 
 	/* Most intel systems have synchronized TSCs except for