From: Chris Lalancette <clalance@redhat.com>
Date: Thu, 5 Mar 2009 14:17:24 +0100
Subject: [x86] xen: silence WRMSR warnings
Message-id: 49AFD0E4.7080505@redhat.com
O-Subject: [RHEL5.4 PATCH]: Silence Xen WRMSR warnings
Bugzilla: 470035
RH-Acked-by: Justin M. Forbes <jforbes@redhat.com>

All,
     In 5.3, the acpi_cpufreq driver was updated to start using the APERF and
MPERF MSR's.  The Xen hypervisor, however, didn't know anything about these
MSR's, so it was denying writes to them.  Besides making it so that the
acpi_cpufreq driver wouldn't properly work under Xen, it would also spew the
following to the xm dmesg logs:

Domain attempted WRMSR 00000000000000e8 from 00000016:3d0e9470 to 00000000:00000000

The attached patch fixes this by implementing the APERF and MPERF MSR writes in
the hypervisor.  This is a backport of xen-unstable c/s 19055, and fixes the
issue for the reporter.  This should resolve BZ 470035.  Please review and ACK.

--
Chris Lalancette

diff --git a/arch/x86/traps.c b/arch/x86/traps.c
index bcf47f4..42d5274 100644
--- a/arch/x86/traps.c
+++ b/arch/x86/traps.c
@@ -1751,6 +1751,12 @@ static int emulate_privileged_op(struct cpu_user_regs *regs)
                  wrmsr_safe(regs->ecx, eax, edx) )
                 goto fail;
             break;
+	case MSR_IA32_MPERF:
+	case MSR_IA32_APERF:
+            if ( (cpufreq_controller != FREQCTL_dom0_kernel) ||
+                 wrmsr_safe(regs->ecx, eax, edx) )
+                goto fail;
+            break;
         default:
             if ( wrmsr_hypervisor_regs(regs->ecx, eax, edx) )
                 break;
diff --git a/include/asm-x86/msr.h b/include/asm-x86/msr.h
index 2638236..3d85857 100644
--- a/include/asm-x86/msr.h
+++ b/include/asm-x86/msr.h
@@ -198,6 +198,9 @@ static inline void write_efer(u64 val)
 #define MSR_IA32_PERF_STATUS		0x198
 #define MSR_IA32_PERF_CTL		0x199
 
+#define MSR_IA32_MPERF			0x000000e7
+#define MSR_IA32_APERF			0x000000e8
+
 #define MSR_IA32_THERM_CONTROL		0x19a
 #define MSR_IA32_THERM_INTERRUPT	0x19b
 #define MSR_IA32_THERM_STATUS		0x19c