Commit 1ba143a5 authored May 24, 2017 by Sebastian Andrzej Siewior Committed by Thomas Gleixner May 26, 2017

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

parent 27d3b157

arch/x86/events/intel/core.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -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;
		}