[PATCH 3/3] perf/x86/amd: Implement x86_pmu::print_debug

[Sandipan Das]

Implement x86_pmu::print_debug for PerfMonV2 capable processors to dump
MSR_AMD64_PERF_CNTR_GLOBAL_{CTL,STATUS}, plus MSR_AMD_DBG_EXTN_CFG if
LBR Extension Version 2 is available. Chain into x86_pmu_print_debug()
afterwards to dump the event selectors and counters.

MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_{CLR,SET} are left out since they are
write-only.

Fixes: 21d59e3e2c40 ("perf/x86/amd/core: Detect PerfMonV2 support")
Reported-by: Petr Tesarik <ptesarik@xxxxxxxx>
Closes: https://lore.kernel.org/all/20260717150315.2868314-1-ptesarik@xxxxxxxx/
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sandipan Das <sandipan.das@xxxxxxx>
---
 arch/x86/events/amd/core.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index a787409f5a62..ecd648af81f7 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -841,6 +841,25 @@ static void amd_pmu_v2_disable_all(void)
 	amd_pmu_check_overflow();
 }
 
+static void amd_pmu_v2_print_debug(int cpu)
+{
+	u64 ctrl, status, debugextn;
+
+	rdmsrq(MSR_AMD64_PERF_CNTR_GLOBAL_CTL, ctrl);
+	rdmsrq(MSR_AMD64_PERF_CNTR_GLOBAL_STATUS, status);
+
+	pr_info("\n");
+	pr_info("CPU#%d: ctrl:       %016llx\n", cpu, ctrl);
+	pr_info("CPU#%d: status:     %016llx\n", cpu, status);
+
+	if (cpu_feature_enabled(X86_FEATURE_AMD_LBR_V2)) {
+		rdmsrq(MSR_AMD_DBG_EXTN_CFG, debugextn);
+		pr_info("CPU#%d: debugextn:  %016llx\n", cpu, debugextn);
+	}
+
+	x86_pmu_print_debug(cpu);
+}
+
 DEFINE_STATIC_CALL_NULL(amd_pmu_branch_add, *x86_pmu.add);
 
 static void amd_pmu_add_event(struct perf_event *event)
@@ -1452,6 +1471,7 @@ static int __init amd_core_pmu_init(void)
 		x86_pmu.disable_all = amd_pmu_v2_disable_all;
 		x86_pmu.enable = amd_pmu_v2_enable_event;
 		x86_pmu.handle_irq = amd_pmu_v2_handle_irq;
+		x86_pmu.print_debug = amd_pmu_v2_print_debug;
 		static_call_update(amd_pmu_test_overflow, amd_pmu_test_overflow_status);
 	}
 
-- 
2.53.0