perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode()

If intel_snb_check_microcode() is invoked via
  microcode_init -> perf_check_microcode -> intel_snb_check_microcode

then get_online_cpus() is invoked nested. This works with the current
implementation of get_online_cpus() but prevents converting it to a percpu
rwsem.

intel_snb_check_microcode() is also invoked from intel_sandybridge_quirk()
unprotected.

Drop get_online_cpus() from intel_snb_check_microcode() and add it to
intel_sandybridge_quirk() so both call sites are protected.

Convert *_online_cpus() to the new interfaces while at it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20170524081548.594862191@linutronix.de

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index a6d91d4..b9174aa 100644 (file)
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3410,12 +3410,10 @@ static void intel_snb_check_microcode(void)
        int pebs_broken = 0;
        int cpu;
 
-       get_online_cpus();
        for_each_online_cpu(cpu) {
                if ((pebs_broken = intel_snb_pebs_broken(cpu)))
                        break;
        }
-       put_online_cpus();
 
        if (pebs_broken == x86_pmu.pebs_broken)
                return;
@@ -3488,7 +3486,9 @@ static bool check_msr(unsigned long msr, u64 mask)
 static __init void intel_sandybridge_quirk(void)
 {
        x86_pmu.check_microcode = intel_snb_check_microcode;
+       cpus_read_lock();
        intel_snb_check_microcode();
+       cpus_read_unlock();
 }
 
 static const struct { int id; char *name; } intel_arch_events_map[] __initconst = {
@@ -4112,13 +4112,12 @@ static __init int fixup_ht_bug(void)
 
        lockup_detector_resume();
 
-       get_online_cpus();
+       cpus_read_lock();
 
-       for_each_online_cpu(c) {
+       for_each_online_cpu(c)
                free_excl_cntrs(c);
-       }
 
-       put_online_cpus();
+       cpus_read_unlock();
        pr_info("PMU erratum BJ122, BV98, HSD29 workaround disabled, HT off\n");
        return 0;
 }