[PATCH V2] riscv: Add BUG_ON() for no cpu nodes in devicetree

[Song Shuai]

When only the ACPI tables are passed to kernel, the tiny devictree created
by EFI Stub doesn't provide cpu nodes.

While if append the "acpi=off" to kernel cmdline to disable ACPI for kernel
the BUG_ON() in of_parse_and_init_cpus() indicates there's no boot cpu
found in the devicetree, not there're no cpu nodes in the devicetree.

Add BUG_ON() in the first place of of_parse_and_init_cpus() to make it clear.

Signed-off-by: Song Shuai <suagrfillet@xxxxxxxxx>
---
Changes since V1:
https://lore.kernel.org/linux-riscv/20230629105839.1160895-1-suagrfillet@xxxxxxxxx/
- revise the commit-msg and move the BUG_ON into of_parse_and_init_cpus() as Conor suggests

---
 arch/riscv/kernel/smpboot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 6ca2b5309aab..04d33afbdf55 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -147,6 +147,8 @@ static void __init of_parse_and_init_cpus(void)
 	int cpuid = 1;
 	int rc;
 
+	BUG_ON(!of_get_next_cpu_node(NULL));
+
 	cpu_set_ops(0);
 
 	for_each_of_cpu_node(dn) {
-- 
2.20.1