perf/x86: Improve debug output in check_hw_exists()

It might be of interest which perfctr msr failed.

Signed-off-by: Robert Richter <robert.richter@amd.com>
[ added hunk to avoid GCC warn ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1340217996-2254-5-git-send-email-robert.richter@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 7b4f1e8..3eb88eb 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -178,7 +178,7 @@ static void release_pmc_hardware(void) {}
 
 static bool check_hw_exists(void)
 {
-       u64 val, val_new = 0;
+       u64 val, val_new = ~0;
        int i, reg, ret = 0;
 
        /*
@@ -211,8 +211,9 @@ static bool check_hw_exists(void)
         * that don't trap on the MSR access and always return 0s.
         */
        val = 0xabcdUL;
-       ret = wrmsrl_safe(x86_pmu_event_addr(0), val);
-       ret |= rdmsrl_safe(x86_pmu_event_addr(0), &val_new);
+       reg = x86_pmu_event_addr(0);
+       ret = wrmsrl_safe(reg, val);
+       ret |= rdmsrl_safe(reg, &val_new);
        if (ret || val != val_new)
                goto msr_fail;
 
@@ -229,6 +230,7 @@ bios_fail:
 
 msr_fail:
        printk(KERN_CONT "Broken PMU hardware detected, using software events only.\n");
+       printk(KERN_ERR "Failed to access perfctr msr (MSR %x is %Lx)\n", reg, val_new);
 
        return false;
 }