target/riscv: Add "pmu-mask" property to replace "pmu-num"

Using a mask instead of the number of PMU devices supports the accurate
emulation of platforms that have a discontinuous set of PMU counters.

The "pmu-num" property now generates a warning when used by the user on
the command line.

Rather than storing the value for "pmu-num" convert it directly to the
mask if it is specified (overwriting the default "pmu-mask" value)
likewise the value is calculated from the mask if the property value is
obtained.

In the unusual situation that both "pmu-mask" and "pmu-num" are provided
then then the order on the command line determines which takes
precedence (later overwriting earlier.)

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231031154000.18134-5-rbradford@rivosinc.com>
[Changes by AF
 - Fixup ext_zihpm logic after rebase
]
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -1427,8 +1427,46 @@ const RISCVCPUMultiExtConfig riscv_cpu_deprecated_exts[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static void prop_pmu_num_set(Object *obj, Visitor *v, const char *name,
+                             void *opaque, Error **errp)
+{
+    RISCVCPU *cpu = RISCV_CPU(obj);
+    uint8_t pmu_num;
+
+    visit_type_uint8(v, name, &pmu_num, errp);
+
+    if (pmu_num > (RV_MAX_MHPMCOUNTERS - 3)) {
+        error_setg(errp, "Number of counters exceeds maximum available");
+        return;
+    }
+
+    if (pmu_num == 0) {
+        cpu->cfg.pmu_mask = 0;
+    } else {
+        cpu->cfg.pmu_mask = MAKE_64BIT_MASK(3, pmu_num);
+    }
+
+    warn_report("\"pmu-num\" property is deprecated; use \"pmu-mask\"");
+}
+
+static void prop_pmu_num_get(Object *obj, Visitor *v, const char *name,
+                             void *opaque, Error **errp)
+{
+    RISCVCPU *cpu = RISCV_CPU(obj);
+    uint8_t pmu_num = ctpop32(cpu->cfg.pmu_mask);
+
+    visit_type_uint8(v, name, &pmu_num, errp);
+}
+
+const PropertyInfo prop_pmu_num = {
+    .name = "pmu-num",
+    .get = prop_pmu_num_get,
+    .set = prop_pmu_num_set,
+};
+
 Property riscv_cpu_options[] = {
-    DEFINE_PROP_UINT8("pmu-num", RISCVCPU, cfg.pmu_num, 16),
+    DEFINE_PROP_UINT32("pmu-mask", RISCVCPU, cfg.pmu_mask, MAKE_64BIT_MASK(3, 16)),
+    {.name = "pmu-num", .info = &prop_pmu_num}, /* Deprecated */
 
     DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true),
     DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true),

target/riscv/cpu_cfg.h

@@ -134,7 +134,7 @@ struct RISCVCPUConfig {
     bool ext_xtheadsync;
     bool ext_XVentanaCondOps;
 
-    uint8_t pmu_num;
+    uint32_t pmu_mask;
     char *priv_spec;
     char *user_spec;
     char *bext_spec;

target/riscv/machine.c

@@ -316,7 +316,7 @@ static bool pmu_needed(void *opaque)
 {
     RISCVCPU *cpu = opaque;
 
-    return cpu->cfg.pmu_num;
+    return (cpu->cfg.pmu_mask > 0);
 }
 
 static const VMStateDescription vmstate_pmu_ctr_state = {

target/riscv/pmu.c

@@ -18,14 +18,13 @@
 
 #include "qemu/osdep.h"
 #include "qemu/log.h"
+#include "qemu/error-report.h"
 #include "cpu.h"
 #include "pmu.h"
 #include "sysemu/cpu-timers.h"
 #include "sysemu/device_tree.h"
 
 #define RISCV_TIMEBASE_FREQ 1000000000 /* 1Ghz */
-#define MAKE_32BIT_MASK(shift, length) \
-        (((uint32_t)(~0UL) >> (32 - (length))) << (shift))
 
 /*
  * To keep it simple, any event can be mapped to any programmable counters in
@@ -184,7 +183,7 @@ int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum riscv_pmu_event_idx event_idx)
     CPURISCVState *env = &cpu->env;
     gpointer value;
 
-    if (!cpu->cfg.pmu_num) {
+    if (!cpu->cfg.pmu_mask) {
         return 0;
     }
     value = g_hash_table_lookup(cpu->pmu_event_ctr_map,
@@ -432,9 +431,12 @@ int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value, uint32_t ctr_idx)
 
 void riscv_pmu_init(RISCVCPU *cpu, Error **errp)
 {
-    uint8_t pmu_num = cpu->cfg.pmu_num;
+    if (cpu->cfg.pmu_mask & (COUNTEREN_CY | COUNTEREN_TM | COUNTEREN_IR)) {
+        error_setg(errp, "\"pmu-mask\" contains invalid bits (0-2) set");
+        return;
+    }
 
-    if (pmu_num > (RV_MAX_MHPMCOUNTERS - 3)) {
+    if (ctpop32(cpu->cfg.pmu_mask) > (RV_MAX_MHPMCOUNTERS - 3)) {
         error_setg(errp, "Number of counters exceeds maximum available");
         return;
     }
@@ -445,6 +447,5 @@ void riscv_pmu_init(RISCVCPU *cpu, Error **errp)
         return;
     }
 
-    /* Create a bitmask of available programmable counters */
+    cpu->pmu_avail_ctrs = cpu->cfg.pmu_mask;
-    cpu->pmu_avail_ctrs = MAKE_32BIT_MASK(3, pmu_num);
 }

target/riscv/tcg/tcg-cpu.c

@@ -600,7 +600,7 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
     }
 
     if (!cpu->cfg.ext_zihpm) {
-        cpu->cfg.pmu_num = 0;
+        cpu->cfg.pmu_mask = 0;
         cpu->pmu_avail_ctrs = 0;
     }
 
@@ -688,7 +688,7 @@ static bool tcg_cpu_realize(CPUState *cs, Error **errp)
         riscv_timer_init(cpu);
     }
 
-    if (cpu->cfg.pmu_num) {
+    if (cpu->cfg.pmu_mask) {
         riscv_pmu_init(cpu, &local_err);
         if (local_err != NULL) {
             error_propagate(errp, local_err);