From: Christopher Lalancette <clalance@redhat.com>
Date: Thu, 7 Jan 2010 20:21:17 -0500
Subject: [xen] fix cpu frequency scaling on Intel procs
Message-id: <4B46423D.3060302@redhat.com>
Patchwork-id: 22345
O-Subject: [RHEL5.5 PATCH Xen]: Fix cpu frequency scaling on Intel
Bugzilla: 553324
RH-Acked-by: Jarod Wilson <jarod@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Don Dutile <ddutile@redhat.com>

All,
     The patch I submitted to fix BZ 502826 broke CPU frequency scaling
on Xen on Intel hosts.  Thanks to Matthew Garrett who pointed out that
I mistakenly masked out the EST flag from dom0, meaning that the dom0
kernel now thinks that CPU frequency scaling is not supported.
     The very simple fix is to stop masking this bit.  This part of the
patch is *not* upstream; I suspect upstream Xen doesn't have/doesn't
notice this problem because frequency scaling is done in the
hypervisor instead of the dom0, but I haven't confirmed.
     Tested by me.  Before this patch, frequency scaling on Intel
hosts would not start.  After this patch, I was able to start frequency
scaling and see the frequency change during load.  This should resolve
BZ 553324.  Please review and ACK.

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/arch/x86/traps.c b/arch/x86/traps.c
index ffc6267..4afc4a1 100644
--- a/arch/x86/traps.c
+++ b/arch/x86/traps.c
@@ -634,7 +634,6 @@ static int emulate_forced_invalid_op(struct cpu_user_regs *regs)
         clear_bit(X86_FEATURE_DSCPL % 32, &c);
         clear_bit(X86_FEATURE_VMXE % 32, &c);
         clear_bit(X86_FEATURE_SMXE % 32, &c);
-        clear_bit(X86_FEATURE_EST % 32, &c);
         clear_bit(X86_FEATURE_TM2 % 32, &c);
         if ( is_pv_32bit_vcpu(current) )
             clear_bit(X86_FEATURE_CX16 % 32, &c);