Intel: perf/x86/intel: Use switch in intel_pmu_disable/enable_event

mainline inclusion
from mainline-v5.10-rc1
commit 58da7dbe
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I47H3V
CVE: NA

--------------------------------

commit 58da7dbe upstream
Backport summary: backport to kernel 4.19.57 for ICX perf topdown support

Currently, the if-else is used in the intel_pmu_disable/enable_event to
check the type of an event. It works well, but with more and more types
added later, e.g., perf metrics, compared to the switch statement, the
if-else may impair the readability of the code.

There is no harm to use the switch statement to replace the if-else
here. Also, some optimizing compilers may compile a switch statement
into a jump-table which is more efficient than if-else for a large
number of cases. The performance gain may not be observed for now,
because the number of cases is only 5, but the benefits may be observed
with more and more types added in the future.

Use switch to replace the if-else in the intel_pmu_disable/enable_event.

If the idx is invalid, print a warning.

For the case INTEL_PMC_IDX_FIXED_BTS in intel_pmu_disable_event, don't
need to check the event->attr.precise_ip. Use return for the case.
Signed-off-by: NKan Liang <kan.liang@linux.intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200723171117.9918-7-kan.liang@linux.intel.comSigned-off-by: NYunying Sun <yunying.sun@intel.com>
Signed-off-by: NJackie Liu <liuyun01@kylinos.cn>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/x86/events/intel/core.c

@@ -2158,17 +2158,27 @@ static void intel_pmu_disable_event(struct perf_event *event)
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
 
-	if (idx < INTEL_PMC_IDX_FIXED) {
+	switch (idx) {
+	case 0 ... INTEL_PMC_IDX_FIXED - 1:
 		intel_clear_masks(event, idx);
 		x86_pmu_disable_event(event);
-	} else if (idx < INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED ... INTEL_PMC_IDX_FIXED_BTS - 1:
 		intel_clear_masks(event, idx);
 		intel_pmu_disable_fixed(event);
-	} else if (idx == INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED_BTS:
 		intel_pmu_disable_bts();
 		intel_pmu_drain_bts_buffer();
-	} else if (idx == INTEL_PMC_IDX_FIXED_VLBR) {
+		return;
+	case INTEL_PMC_IDX_FIXED_VLBR:
+		intel_clear_masks(event, idx);
+		break;
+	default:
 		intel_clear_masks(event, idx);
+		pr_warn("Failed to disable the event with invalid index %d\n",
+			idx);
+		return;
 	}
 
 	/*
@@ -2241,18 +2251,26 @@ static void intel_pmu_enable_event(struct perf_event *event)
 	if (unlikely(event->attr.precise_ip))
 		intel_pmu_pebs_enable(event);
 
-	if (idx < INTEL_PMC_IDX_FIXED) {
+	switch (idx) {
+	case 0 ... INTEL_PMC_IDX_FIXED - 1:
 		intel_set_masks(event, idx);
 		__x86_pmu_enable_event(hwc, ARCH_PERFMON_EVENTSEL_ENABLE);
-	} else if (idx < INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED ... INTEL_PMC_IDX_FIXED_BTS - 1:
 		intel_set_masks(event, idx);
 		intel_pmu_enable_fixed(event);
-	} else if (idx == INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED_BTS:
 		if (!__this_cpu_read(cpu_hw_events.enabled))
 			return;
 		intel_pmu_enable_bts(hwc->config);
-	} else if (idx == INTEL_PMC_IDX_FIXED_VLBR) {
+		break;
+	case INTEL_PMC_IDX_FIXED_VLBR:
 		intel_set_masks(event, idx);
+		break;
+	default:
+		pr_warn("Failed to enable the event with invalid index %d\n",
+			idx);
 	}
 }