target/loongarch/kvm: Implement LoongArch PMU extension

Implement PMU extension for LoongArch kvm mode. Use OnOffAuto type
variable pmu to check the PMU feature. If the PMU Feature is not supported
with KVM host, it reports error if there is pmu=on command line.

If there is no any command line about pmu parameter, it checks whether
KVM host supports the PMU Feature and set the corresponding value in cpucfg.

This patch is based on lbt patch located at
  https://lore.kernel.org/qemu-devel/20240904061859.86615-1-maobibo@loongson.cn

Co-developed-by: Song Gao <gaosong@loongson.cn>
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240918082315.2345034-1-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>

target/loongarch/cpu.c

@@ -676,6 +676,18 @@ static void loongarch_set_lbt(Object *obj, bool value, Error **errp)
     cpu->lbt = value ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
 }
 
+static bool loongarch_get_pmu(Object *obj, Error **errp)
+{
+    return LOONGARCH_CPU(obj)->pmu != ON_OFF_AUTO_OFF;
+}
+
+static void loongarch_set_pmu(Object *obj, bool value, Error **errp)
+{
+    LoongArchCPU *cpu = LOONGARCH_CPU(obj);
+
+    cpu->pmu = value ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
+}
+
 void loongarch_cpu_post_init(Object *obj)
 {
     LoongArchCPU *cpu = LOONGARCH_CPU(obj);
@@ -691,6 +703,13 @@ void loongarch_cpu_post_init(Object *obj)
                                  loongarch_set_lbt);
         object_property_set_description(obj, "lbt",
                                    "Set off to disable Binary Tranlation.");
+
+        cpu->pmu = ON_OFF_AUTO_AUTO;
+        object_property_add_bool(obj, "pmu", loongarch_get_pmu,
+                                 loongarch_set_pmu);
+        object_property_set_description(obj, "pmu",
+                                   "Set off to performance monitor unit.");
+
     } else {
         cpu->lbt = ON_OFF_AUTO_OFF;
     }

target/loongarch/cpu.h

@@ -284,6 +284,7 @@ typedef struct LoongArchTLB LoongArchTLB;
 
 enum loongarch_features {
     LOONGARCH_FEATURE_LBT, /* loongson binary translation extension */
+    LOONGARCH_FEATURE_PMU,
 };
 
 typedef struct  LoongArchBT {
@@ -399,6 +400,7 @@ struct ArchCPU {
     QEMUTimer timer;
     uint32_t  phy_id;
     OnOffAuto lbt;
+    OnOffAuto pmu;
 
     /* 'compatible' string for this CPU for Linux device trees */
     const char *dtb_compatible;

target/loongarch/kvm/kvm.c

@@ -750,9 +750,18 @@ static bool kvm_feature_supported(CPUState *cs, enum loongarch_features feature)
         attr.attr = KVM_LOONGARCH_VM_FEAT_MIPSBT;
         ret |= kvm_vm_ioctl(kvm_state, KVM_HAS_DEVICE_ATTR, &attr);
         return (ret == 0);
+
+    case LOONGARCH_FEATURE_PMU:
+        attr.group = KVM_LOONGARCH_VM_FEAT_CTRL;
+        attr.attr = KVM_LOONGARCH_VM_FEAT_PMU;
+        ret = kvm_vm_ioctl(kvm_state, KVM_HAS_DEVICE_ATTR, &attr);
+        return (ret == 0);
+
     default:
         return false;
     }
+
+    return false;
 }
 
 static int kvm_cpu_check_lbt(CPUState *cs, Error **errp)
@@ -776,6 +785,32 @@ static int kvm_cpu_check_lbt(CPUState *cs, Error **errp)
     return 0;
 }
 
+static int kvm_cpu_check_pmu(CPUState *cs, Error **errp)
+{
+    LoongArchCPU *cpu = LOONGARCH_CPU(cs);
+    CPULoongArchState *env = cpu_env(cs);
+    bool kvm_supported;
+
+    kvm_supported = kvm_feature_supported(cs, LOONGARCH_FEATURE_PMU);
+    if (cpu->pmu == ON_OFF_AUTO_ON) {
+        if (!kvm_supported) {
+            error_setg(errp, "'pmu' feature not supported by KVM on the host");
+            return -ENOTSUP;
+        }
+    } else if (cpu->pmu != ON_OFF_AUTO_AUTO) {
+        /* disable pmu if ON_OFF_AUTO_OFF is set */
+        kvm_supported = false;
+    }
+
+    if (kvm_supported) {
+        env->cpucfg[6] = FIELD_DP32(env->cpucfg[6], CPUCFG6, PMP, 1);
+        env->cpucfg[6] = FIELD_DP32(env->cpucfg[6], CPUCFG6, PMNUM, 3);
+        env->cpucfg[6] = FIELD_DP32(env->cpucfg[6], CPUCFG6, PMBITS, 63);
+        env->cpucfg[6] = FIELD_DP32(env->cpucfg[6], CPUCFG6, UPM, 1);
+    }
+    return 0;
+}
+
 int kvm_arch_init_vcpu(CPUState *cs)
 {
     uint64_t val;
@@ -793,6 +828,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
     if (ret < 0) {
         error_report_err(local_err);
     }
+
+    ret = kvm_cpu_check_pmu(cs, &local_err);
+    if (ret < 0) {
+        error_report_err(local_err);
+    }
+
     return ret;
 }
 

target/loongarch/loongarch-qmp-cmds.c

@@ -40,7 +40,7 @@ CpuDefinitionInfoList *qmp_query_cpu_definitions(Error **errp)
 }
 
 static const char *cpu_model_advertised_features[] = {
-    "lsx", "lasx", "lbt", NULL
+    "lsx", "lasx", "lbt", "pmu", NULL
 };
 
 CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,