perf/x86: Add a macro for RDPMC offset of fixed counters

The RDPMC base offset of fixed counters is hard-code. Use a meaningful
name to replace the magic number to improve the readability of the code.
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200723171117.9918-10-kan.liang@linux.intel.com

arch/x86/events/core.c

@@ -1151,7 +1151,8 @@ static inline void x86_assign_hw_event(struct perf_event *event,
 		hwc->config_base = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
 		hwc->event_base = MSR_ARCH_PERFMON_FIXED_CTR0 +
 				(idx - INTEL_PMC_IDX_FIXED);
-		hwc->event_base_rdpmc = (idx - INTEL_PMC_IDX_FIXED) | 1<<30;
+		hwc->event_base_rdpmc = (idx - INTEL_PMC_IDX_FIXED) |
+					INTEL_PMC_FIXED_RDPMC_BASE;
 		break;
 
 	default:

arch/x86/include/asm/perf_event.h

@@ -196,6 +196,9 @@ struct x86_pmu_capability {
  * Fixed-purpose performance events:
  */
 
+/* RDPMC offset for Fixed PMCs */
+#define INTEL_PMC_FIXED_RDPMC_BASE		(1 << 30)
+
 /*
  * All the fixed-mode PMCs are configured via this single MSR:
  */