perf_counter: fix crash on perfmon v1 systems

Impact: fix boot crash on Intel Perfmon Version 1 systems

Intel Perfmon v1 does not support the global MSRs, nor does
it offer the generalized MSR ranges. So support v2 and later
CPUs only.

Also mark pmc_ops as read-mostly - to avoid false cacheline
sharing.

Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 5 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 22dab06c08a4..6cba9d47b711 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -57,12 +57,14 @@ struct pmc_x86_ops {
         int             max_events;
 };
 
-static struct pmc_x86_ops *pmc_ops;
+static struct pmc_x86_ops *pmc_ops __read_mostly;
 
 static DEFINE_PER_CPU(struct cpu_hw_counters, cpu_hw_counters) = {
         .enabled = 1,
 };
 
+static __read_mostly int intel_perfmon_version;
+
 /*
  * Intel PerfMon v3. Used on Core2 and later.
  */
@@ -613,7 +615,7 @@ void perf_counter_print_debug(void)
         cpu = smp_processor_id();
         cpuc = &per_cpu(cpu_hw_counters, cpu);
 
-        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
+        if (intel_perfmon_version >= 2) {
                 rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, ctrl);
                 rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status);
                 rdmsrl(MSR_CORE_PERF_GLOBAL_OVF_CTRL, overflow);
@@ -930,10 +932,10 @@ static struct pmc_x86_ops pmc_amd_ops = {
 
 static struct pmc_x86_ops *pmc_intel_init(void)
 {
+        union cpuid10_edx edx;
         union cpuid10_eax eax;
-        unsigned int ebx;
         unsigned int unused;
-        union cpuid10_edx edx;
+        unsigned int ebx;
 
         /*
          * Check whether the Architectural PerfMon supports
@@ -943,8 +945,12 @@ static struct pmc_x86_ops *pmc_intel_init(void)
         if (eax.split.mask_length <= ARCH_PERFMON_BRANCH_MISSES_RETIRED)
                 return NULL;
 
+        intel_perfmon_version = eax.split.version_id;
+        if (intel_perfmon_version < 2)
+                return NULL;
+
         pr_info("Intel Performance Monitoring support detected.\n");
-        pr_info("... version:         %d\n", eax.split.version_id);
+        pr_info("... version:         %d\n", intel_perfmon_version);
         pr_info("... bit width:       %d\n", eax.split.bit_width);
         pr_info("... mask length:     %d\n", eax.split.mask_length);