hw/riscv/riscv-iommu: instantiate hpm_timer

The next HPM related changes requires the HPM overflow timer to be
initialized by the riscv-iommu base emulation.

Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250224190826.1858473-6-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/riscv-iommu-hpm.c

@@ -166,3 +166,39 @@ void riscv_iommu_hpm_incr_ctr(RISCVIOMMUState *s, RISCVIOMMUContext *ctx,
         hpm_incr_ctr(s, ctr_idx);
     }
 }
+
+/* Timer callback for cycle counter overflow. */
+void riscv_iommu_hpm_timer_cb(void *priv)
+{
+    RISCVIOMMUState *s = priv;
+    const uint32_t inhibit = riscv_iommu_reg_get32(
+        s, RISCV_IOMMU_REG_IOCOUNTINH);
+    uint32_t ovf;
+
+    if (get_field(inhibit, RISCV_IOMMU_IOCOUNTINH_CY)) {
+        return;
+    }
+
+    if (s->irq_overflow_left > 0) {
+        uint64_t irq_trigger_at =
+            qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + s->irq_overflow_left;
+        timer_mod_anticipate_ns(s->hpm_timer, irq_trigger_at);
+        s->irq_overflow_left = 0;
+        return;
+    }
+
+    ovf = riscv_iommu_reg_get32(s, RISCV_IOMMU_REG_IOCOUNTOVF);
+    if (!get_field(ovf, RISCV_IOMMU_IOCOUNTOVF_CY)) {
+        /*
+         * We don't need to set hpmcycle_val to zero and update hpmcycle_prev to
+         * current clock value. The way we calculate iohpmcycs will overflow
+         * and return the correct value. This avoids the need to synchronize
+         * timer callback and write callback.
+         */
+        riscv_iommu_reg_mod32(s, RISCV_IOMMU_REG_IOCOUNTOVF,
+            RISCV_IOMMU_IOCOUNTOVF_CY, 0);
+        riscv_iommu_reg_mod64(s, RISCV_IOMMU_REG_IOHPMCYCLES,
+            RISCV_IOMMU_IOHPMCYCLES_OVF, 0);
+        riscv_iommu_notify(s, RISCV_IOMMU_INTR_PM);
+    }
+}

hw/riscv/riscv-iommu-hpm.h

@@ -25,5 +25,6 @@
 uint64_t riscv_iommu_hpmcycle_read(RISCVIOMMUState *s);
 void riscv_iommu_hpm_incr_ctr(RISCVIOMMUState *s, RISCVIOMMUContext *ctx,
                               unsigned event_id);
+void riscv_iommu_hpm_timer_cb(void *priv);
 
 #endif

hw/riscv/riscv-iommu.c

@@ -2382,6 +2382,8 @@ static void riscv_iommu_realize(DeviceState *dev, Error **errp)
     address_space_init(&s->trap_as, &s->trap_mr, "riscv-iommu-trap-as");
 
     if (s->cap & RISCV_IOMMU_CAP_HPM) {
+        s->hpm_timer =
+            timer_new_ns(QEMU_CLOCK_VIRTUAL, riscv_iommu_hpm_timer_cb, s);
         s->hpm_event_ctr_map = g_hash_table_new(g_direct_hash, g_direct_equal);
     }
 }
@@ -2395,6 +2397,7 @@ static void riscv_iommu_unrealize(DeviceState *dev)
 
     if (s->cap & RISCV_IOMMU_CAP_HPM) {
         g_hash_table_unref(s->hpm_event_ctr_map);
+        timer_free(s->hpm_timer);
     }
 }
 

hw/riscv/riscv-iommu.h

@@ -83,8 +83,10 @@ struct RISCVIOMMUState {
     QLIST_HEAD(, RISCVIOMMUSpace) spaces;
 
     /* HPM cycle counter */
+    QEMUTimer *hpm_timer;
     uint64_t hpmcycle_val;      /* Current value of cycle register */
     uint64_t hpmcycle_prev;     /* Saved value of QEMU_CLOCK_VIRTUAL clock */
+    uint64_t irq_overflow_left; /* Value beyond INT64_MAX after overflow */
 
     /* HPM event counters */
     GHashTable *hpm_event_ctr_map; /* Mapping of events to counters */