1 files changed, 12 insertions, 4 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 915b876edd1..4a3374e61a9 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -208,12 +208,14 @@ static bool check_hw_exists(void)
         }
 
         /*
-         * Now write a value and read it back to see if it matches,
-         * this is needed to detect certain hardware emulators (qemu/kvm)
-         * that don't trap on the MSR access and always return 0s.
+         * Read the current value, change it and read it back to see if it
+         * matches, this is needed to detect certain hardware emulators
+         * (qemu/kvm) that don't trap on the MSR access and always return 0s.
          */
-        val = 0xabcdUL;
         reg = x86_pmu_event_addr(0);
+        if (rdmsrl_safe(reg, &val))
+                goto msr_fail;
+        val ^= 0xffffUL;
         ret = wrmsrl_safe(reg, val);
         ret |= rdmsrl_safe(reg, &val_new);
         if (ret || val != val_new)
@@ -338,6 +340,9 @@ int x86_setup_perfctr(struct perf_event *event)
                 /* BTS is currently only allowed for user-mode. */
                 if (!attr->exclude_kernel)
                         return -EOPNOTSUPP;
+
+                if (!attr->exclude_guest)
+                        return -EOPNOTSUPP;
         }
 
         hwc->config |= config;
@@ -380,6 +385,9 @@ int x86_pmu_hw_config(struct perf_event *event)
         if (event->attr.precise_ip) {
                 int precise = 0;
 
+                if (!event->attr.exclude_guest)
+                        return -EOPNOTSUPP;
+
                 /* Support for constant skid */
                 if (x86_pmu.pebs_active && !x86_pmu.pebs_broken) {
                         precise++;