Two x86 PMU fixes:

- Work around AMD erratum to filter out bogus LBR stack entries
 
  - Fix incorrect PMU reset that can result in warnings (or worse)
    during suspend/hibernation.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'perf-urgent-2024-03-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 perf event fixes from Ingo Molnar:

 - Work around AMD erratum to filter out bogus LBR stack entries

 - Fix incorrect PMU reset that can result in warnings (or worse)
   during suspend/hibernation

* tag 'perf-urgent-2024-03-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/amd/core: Avoid register reset when CPU is dead
  perf/x86/amd/lbr: Discard erroneous branch entries

arch/x86/events/amd/core.c

@@ -604,7 +604,6 @@ static void amd_pmu_cpu_dead(int cpu)
 
 	kfree(cpuhw->lbr_sel);
 	cpuhw->lbr_sel = NULL;
-	amd_pmu_cpu_reset(cpu);
 
 	if (!x86_pmu.amd_nb_constraints)
 		return;

arch/x86/events/amd/lbr.c

@@ -173,9 +173,11 @@ void amd_pmu_lbr_read(void)
 
 		/*
 		 * Check if a branch has been logged; if valid = 0, spec = 0
-		 * then no branch was recorded
+		 * then no branch was recorded; if reserved = 1 then an
+		 * erroneous branch was recorded (see Erratum 1452)
 		 */
-		if (!entry.to.split.valid && !entry.to.split.spec)
+		if ((!entry.to.split.valid && !entry.to.split.spec) ||
+		    entry.to.split.reserved)
 			continue;
 
 		perf_clear_branch_entry_bitfields(br + out);