riscv: sifive_u: Update the plic hart config to support multicore

At present the PLIC is instantiated to support only one hart, while
the machine allows at most 4 harts to be created. When more than 1
hart is configured, PLIC needs to instantiated to support multicore,
otherwise an SMP OS does not work.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

hw/riscv/sifive_u.c

@@ -344,6 +344,8 @@ static void riscv_sifive_u_soc_realize(DeviceState *dev, Error **errp)
     MemoryRegion *system_memory = get_system_memory();
     MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
     qemu_irq plic_gpios[SIFIVE_U_PLIC_NUM_SOURCES];
+    char *plic_hart_config;
+    size_t plic_hart_config_len;
     int i;
     Error *err = NULL;
     NICInfo *nd = &nd_table[0];
@@ -357,9 +359,21 @@ static void riscv_sifive_u_soc_realize(DeviceState *dev, Error **errp)
     memory_region_add_subregion(system_memory, memmap[SIFIVE_U_MROM].base,
                                 mask_rom);
 
+    /* create PLIC hart topology configuration string */
+    plic_hart_config_len = (strlen(SIFIVE_U_PLIC_HART_CONFIG) + 1) * smp_cpus;
+    plic_hart_config = g_malloc0(plic_hart_config_len);
+    for (i = 0; i < smp_cpus; i++) {
+        if (i != 0) {
+            strncat(plic_hart_config, ",", plic_hart_config_len);
+        }
+        strncat(plic_hart_config, SIFIVE_U_PLIC_HART_CONFIG,
+                plic_hart_config_len);
+        plic_hart_config_len -= (strlen(SIFIVE_U_PLIC_HART_CONFIG) + 1);
+    }
+
     /* MMIO */
     s->plic = sifive_plic_create(memmap[SIFIVE_U_PLIC].base,
-        (char *)SIFIVE_U_PLIC_HART_CONFIG,
+        plic_hart_config,
         SIFIVE_U_PLIC_NUM_SOURCES,
         SIFIVE_U_PLIC_NUM_PRIORITIES,
         SIFIVE_U_PLIC_PRIORITY_BASE,