target/arm: Add array for supported PMU events, generate PMCEID[01]_EL0

This commit doesn't add any supported events, but provides the framework
for adding them. We store the pm_event structs in a simple array, and
provide the mapping from the event numbers to array indexes in the
supported_event_map array. Because the value of PMCEID[01] depends upon
which events are supported at runtime, generate it dynamically.

Backports commit 57a4a11b2b281bb548b419ca81bfafb214e4c77a from qemu

qemu/aarch64.h

@@ -3301,6 +3301,7 @@
 #define fp_exception_el fp_exception_el_aarch64
 #define gen_a64_set_pc_im gen_a64_set_pc_im_aarch64
 #define gen_cmtst_i64 gen_cmtst_i64_aarch64
+#define get_pmceid get_pmceid_aarch64
 #define helper_advsimd_acge_f16 helper_advsimd_acge_f16_aarch64
 #define helper_advsimd_acgt_f16 helper_advsimd_acgt_f16_aarch64
 #define helper_advsimd_add2h helper_advsimd_add2h_aarch64

qemu/aarch64eb.h

@@ -3301,6 +3301,7 @@
 #define fp_exception_el fp_exception_el_aarch64eb
 #define gen_a64_set_pc_im gen_a64_set_pc_im_aarch64eb
 #define gen_cmtst_i64 gen_cmtst_i64_aarch64eb
+#define get_pmceid get_pmceid_aarch64eb
 #define helper_advsimd_acge_f16 helper_advsimd_acge_f16_aarch64eb
 #define helper_advsimd_acgt_f16 helper_advsimd_acgt_f16_aarch64eb
 #define helper_advsimd_add2h helper_advsimd_add2h_aarch64eb

qemu/arm.h

@@ -3286,6 +3286,7 @@
 #define cmtst_op cmtst_op_arm
 #define fp_exception_el fp_exception_el_arm
 #define gen_cmtst_i64 gen_cmtst_i64_arm
+#define get_pmceid get_pmceid_arm
 #define mla_op mla_op_arm
 #define mls_op mls_op_arm
 #define pmccntr_op_start pmccntr_op_start_arm

qemu/armeb.h

@@ -3286,6 +3286,7 @@
 #define cmtst_op cmtst_op_armeb
 #define fp_exception_el fp_exception_el_armeb
 #define gen_cmtst_i64 gen_cmtst_i64_armeb
+#define get_pmceid get_pmceid_armeb
 #define mla_op mla_op_armeb
 #define mls_op mls_op_armeb
 #define pmccntr_op_start pmccntr_op_start_armeb

qemu/header_gen.py

@@ -3295,6 +3295,7 @@ arm_symbols = (
     'cmtst_op',
     'fp_exception_el',
     'gen_cmtst_i64',
+    'get_pmceid',
     'mla_op',
     'mls_op',
     'pmccntr_op_start',
@@ -3346,6 +3347,7 @@ aarch64_symbols = (
     'fp_exception_el',
     'gen_a64_set_pc_im',
     'gen_cmtst_i64',
+    'get_pmceid',
     'helper_advsimd_acge_f16',
     'helper_advsimd_acgt_f16',
     'helper_advsimd_add2h',

qemu/target/arm/cpu.c

@@ -761,15 +761,19 @@ static int arm_cpu_realizefn(struct uc_struct *uc, DeviceState *dev, Error **err
 
     if (!cpu->has_pmu) {
         unset_feature(env, ARM_FEATURE_PMU);
-        cpu->id_aa64dfr0 &= ~0xf00;
     }
-    // Unicorn: Commented out
-#if 0
-    else if (!kvm_enabled()) {
+
+    if (arm_feature(env, ARM_FEATURE_PMU)) {
+        cpu->pmceid0 = get_pmceid(&cpu->env, 0);
+        cpu->pmceid1 = get_pmceid(&cpu->env, 1);
+
         arm_register_pre_el_change_hook(cpu, &pmu_pre_el_change, 0);
         arm_register_el_change_hook(cpu, &pmu_post_el_change, 0);
+    } else {
+        cpu->id_aa64dfr0 &= ~0xf00;
+        cpu->pmceid0 = 0;
+        cpu->pmceid1 = 0;
     }
-#endif
 
     if (!arm_feature(env, ARM_FEATURE_EL2)) {
         /* Disable the hypervisor feature bits in the processor feature
@@ -1410,8 +1414,6 @@ static void cortex_a7_initfn(struct uc_struct *uc, Object *obj, void *opaque)
     cpu->id_pfr0 = 0x00001131;
     cpu->id_pfr1 = 0x00011011;
     cpu->id_dfr0 = 0x02010555;
-    cpu->pmceid0 = 0x00000000;
-    cpu->pmceid1 = 0x00000000;
     cpu->id_afr0 = 0x00000000;
     cpu->id_mmfr0 = 0x10101105;
     cpu->id_mmfr1 = 0x40000000;
@@ -1457,8 +1459,6 @@ static void cortex_a15_initfn(struct uc_struct *uc, Object *obj, void *opaque)
     cpu->id_pfr0 = 0x00001131;
     cpu->id_pfr1 = 0x00011011;
     cpu->id_dfr0 = 0x02010555;
-    cpu->pmceid0 = 0x00000000;
-    cpu->pmceid1 = 0x00000000;
     cpu->id_afr0 = 0x00000000;
     cpu->id_mmfr0 = 0x10201105;
     cpu->id_mmfr1 = 0x20000000;

qemu/target/arm/cpu.h

@@ -671,6 +671,17 @@ typedef struct CPUARMState {
     /* Store GICv3CPUState to access from this struct */
     void *gicv3state;
 
+    // Note: The event map has been moved here in Unicorn to avoid non-const file-static state.
+
+    /*
+     * Note: Before increasing MAX_EVENT_ID beyond 0x3f into the 0x40xx range of
+     * events (i.e. the statistical profiling extension), this implementation
+     * should first be updated to something sparse instead of the current
+     * supported_event_map[] array.
+     */
+#define MAX_EVENT_ID 0x0
+    uint16_t supported_event_map[MAX_EVENT_ID + 1];
+
     // Unicorn engine
     struct uc_struct *uc;
 } CPUARMState;
@@ -949,6 +960,16 @@ void pmu_op_finish(CPUARMState *env);
 void pmu_pre_el_change(ARMCPU *cpu, void *ignored);
 void pmu_post_el_change(ARMCPU *cpu, void *ignored);
 
+/*
+ * get_pmceid
+ * @env: CPUARMState
+ * @which: which PMCEID register to return (0 or 1)
+ *
+ * Return the PMCEID[01]_EL0 register values corresponding to the counters
+ * which are supported given the current configuration
+ */
+uint64_t get_pmceid(CPUARMState *env, unsigned which);
+
 /* SCTLR bit meanings. Several bits have been reused in newer
  * versions of the architecture; in that case we define constants
  * for both old and new bit meanings. Code which tests against those

qemu/target/arm/cpu64.c

@@ -118,8 +118,6 @@ static void aarch64_a57_initfn(struct uc_struct *uc, Object *obj, void *opaque)
     cpu->isar.id_isar6 = 0;
     cpu->isar.id_aa64pfr0 = 0x00002222;
     cpu->id_aa64dfr0 = 0x10305106;
-    cpu->pmceid0 = 0x00000000;
-    cpu->pmceid1 = 0x00000000;
     cpu->isar.id_aa64isar0 = 0x00011120;
     cpu->isar.id_aa64mmfr0 = 0x00001124;
     cpu->dbgdidr = 0x3516d000;
@@ -220,8 +218,6 @@ static void aarch64_a72_initfn(struct uc_struct *uc, Object *obj, void *opaque)
     cpu->isar.id_isar5 = 0x00011121;
     cpu->isar.id_aa64pfr0 = 0x00002222;
     cpu->id_aa64dfr0 = 0x10305106;
-    cpu->pmceid0 = 0x00000000;
-    cpu->pmceid1 = 0x00000000;
     cpu->isar.id_aa64isar0 = 0x00011120;
     cpu->isar.id_aa64mmfr0 = 0x00001124;
     cpu->dbgdidr = 0x3516d000;

qemu/target/arm/helper.c

@@ -873,6 +873,55 @@ static inline uint64_t pmu_counter_mask(CPUARMState *env)
   return (1 << 31) | ((1 << pmu_num_counters(env)) - 1);
 }
 
+typedef struct pm_event {
+    uint16_t number; /* PMEVTYPER.evtCount is 16 bits wide */
+    /* If the event is supported on this CPU (used to generate PMCEID[01]) */
+    bool (*supported)(CPUARMState *);
+    /*
+     * Retrieve the current count of the underlying event. The programmed
+     * counters hold a difference from the return value from this function
+     */
+    uint64_t (*get_count)(CPUARMState *);
+} pm_event;
+
+static const pm_event pm_events[] = {
+};
+
+#define UNSUPPORTED_EVENT UINT16_MAX
+
+/*
+ * Called upon initialization to build PMCEID0_EL0 or PMCEID1_EL0 (indicated by
+ * 'which'). We also use it to build a map of ARM event numbers to indices in
+ * our pm_events array.
+ *
+ * Note: Events in the 0x40XX range are not currently supported.
+ */
+uint64_t get_pmceid(CPUARMState *env, unsigned which)
+{
+    uint64_t pmceid = 0;
+    unsigned int i;
+
+    assert(which <= 1);
+
+    for (i = 0; i < ARRAY_SIZE(env->supported_event_map); i++) {
+        env->supported_event_map[i] = UNSUPPORTED_EVENT;
+    }
+
+    for (i = 0; i < ARRAY_SIZE(pm_events); i++) {
+        const pm_event *cnt = &pm_events[i];
+        assert(cnt->number <= MAX_EVENT_ID);
+        /* We do not currently support events in the 0x40xx range */
+        assert(cnt->number <= 0x3f);
+
+        if ((cnt->number & 0x20) == (which << 6) &&
+                cnt->supported(env)) {
+            pmceid |= (1 << (cnt->number & 0x1f));
+            env->supported_event_map[cnt->number] = i;
+        }
+    }
+    return pmceid;
+}
+
 static CPAccessResult pmreg_access(CPUARMState *env, const ARMCPRegInfo *ri,
                                    bool isread)
 {