x86, perf, nmi: Disable perf if counters are not accessible

[mv-sheeva.git] / arch / x86 / kernel / cpu / perf_event.c

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index ed6310183efb4337de7489362b350f81031ca2c8..6d75b9145b13f0e68a106acd76b0d458c827d099 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -381,6 +381,20 @@ static void release_pmc_hardware(void) {}
 
 #endif
 
+static bool check_hw_exists(void)
+{
+       u64 val, val_new = 0;
+       int ret = 0;
+
+       val = 0xabcdUL;
+       ret |= checking_wrmsrl(x86_pmu.perfctr, val);
+       ret |= rdmsrl_safe(x86_pmu.perfctr, &val_new);
+       if (ret || val != val_new)
+               return false;
+
+       return true;
+}
+
 static void reserve_ds_buffers(void);
 static void release_ds_buffers(void);
 
@@ -1372,6 +1386,12 @@ void __init init_hw_perf_events(void)
 
        pmu_check_apic();
 
+       /* sanity check that the hardware exists or is emulated */
+       if (!check_hw_exists()) {
+               pr_cont("Broken PMU hardware detected, software events only.\n");
+               return;
+       }
+
        pr_cont("%s PMU driver.\n", x86_pmu.name);
 
        if (x86_pmu.quirks)