x86/VPMU: disable when NMI watchdog is on

NMI watchdog sets APIC_LVTPC register to generate an NMI when PMU counter
overflow occurs. This may be overwritten by VPMU code later, effectively
turning off the watchdog.

We should disable VPMU when NMI watchdog is running.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: e5e09b5c46
master date: 2015-02-03 11:30:09 +0100

docs/misc/xen-command-line.markdown

@@ -981,6 +981,8 @@ wrong behaviour (see handle\_pmc\_quirk()).
 If 'vpmu=bts' is specified the virtualisation of the Branch Trace Store (BTS)
 feature is switched on on Intel processors supporting this feature.
 
+Note that if **watchdog** option is also specified vpmu will be turned off.
+
 *Warning:*
 As the BTS virtualisation is not 100% safe and because of the nehalem quirk
 don't use the vpmu flag on production systems with Intel cpus!

xen/arch/x86/hvm/vpmu.c

@@ -24,6 +24,7 @@
 #include <asm/regs.h>
 #include <asm/types.h>
 #include <asm/msr.h>
+#include <asm/nmi.h>
 #include <asm/hvm/support.h>
 #include <asm/hvm/vmx/vmx.h>
 #include <asm/hvm/vmx/vmcs.h>
@@ -284,3 +285,15 @@ void vpmu_dump(struct vcpu *v)
         vpmu->arch_vpmu_ops->arch_vpmu_dump(v);
 }
 
+static int __init vpmu_init(void)
+{
+    /* NMI watchdog uses LVTPC and HW counter */
+    if ( opt_watchdog && opt_vpmu_enabled )
+    {
+        printk(XENLOG_WARNING "NMI watchdog is enabled. Turning VPMU off.\n");
+        opt_vpmu_enabled = 0;
+    }
+
+    return 0;
+}
+__initcall(vpmu_init);