RISC-V: Support nr_cpus command line option.

If nr_cpus command line option is set, maximum possible cpu should be
set to that value.
Signed-off-by: NAtish Patra <atish.patra@wdc.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

arch/riscv/kernel/smpboot.c

@@ -84,11 +84,19 @@ void __init setup_smp(void)
 		}
 
 		cpuid_to_hartid_map(cpuid) = hart;
-		set_cpu_possible(cpuid, true);
 		cpuid++;
 	}
 
 	BUG_ON(!found_boot_cpu);
+
+	if (cpuid > nr_cpu_ids)
+		pr_warn("Total number of cpus [%d] is greater than nr_cpus option value [%d]\n",
+			cpuid, nr_cpu_ids);
+
+	for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
+		if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID)
+			set_cpu_possible(cpuid, true);
+	}
 }
 
 int __cpu_up(unsigned int cpu, struct task_struct *tidle)