[rtems commit] bsps/riscv: Make SMP start more robust

[Sebastian Huber]

Module:    rtems
Branch:    master
Commit:    e5233057be3396e9cd75ffd3a92d2048df316a4b
Changeset: http://git.rtems.org/rtems/commit/?id=e5233057be3396e9cd75ffd3a92d2048df316a4b

Author:    Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:      Thu Mar 16 08:31:08 2023 +0100

bsps/riscv: Make SMP start more robust

In SMP configurations, check that we run on a configured processor.  If not,
then there is not much that can be done since we do not have a stack available
for this processor.  Just loop forever in this case.  Do this in assemlby to
ensure that no stack memory is used.

---

 bsps/riscv/riscv/start/bspsmp.c |  5 +----
 bsps/riscv/shared/start/start.S | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/bsps/riscv/riscv/start/bspsmp.c b/bsps/riscv/riscv/start/bspsmp.c
index 91f4f7b96a..ce5792f5b8 100644
--- a/bsps/riscv/riscv/start/bspsmp.c
+++ b/bsps/riscv/riscv/start/bspsmp.c
@@ -36,10 +36,7 @@ void bsp_start_on_secondary_processor(Per_CPU_Control *cpu_self)
 
   cpu_index_self = _Per_CPU_Get_index(cpu_self);
 
-  if (
-    cpu_index_self < rtems_configuration_get_maximum_processors()
-      && _SMP_Should_start_processor(cpu_index_self)
-  ) {
+  if (_SMP_Should_start_processor(cpu_index_self)) {
     set_csr(mie, MIP_MSIP | MIP_MEIP);
     _SMP_Start_multitasking_on_secondary_processor(cpu_self);
   } else {
diff --git a/bsps/riscv/shared/start/start.S b/bsps/riscv/shared/start/start.S
index 34e1839ca1..242bd4fcc4 100644
--- a/bsps/riscv/shared/start/start.S
+++ b/bsps/riscv/shared/start/start.S
@@ -66,8 +66,17 @@ SYM(_start):
 	LADDR	sp, _ISR_Stack_area_begin
 	LADDR	t2, _ISR_Stack_size
 	csrr	s0, mhartid
-	li      t3, RISCV_BOOT_HARTID
-	sub     s0, s0, t3
+	li	t3, RISCV_BOOT_HARTID
+	sub	s0, s0, t3
+
+	/*
+	 * Check that this is a configured processor.  If not, then there is
+	 * not much that can be done since we do not have a stack available for
+	 * this processor.  Just loop forever in this case.
+	 */
+	LREG	t3, _SMP_Processor_configured_maximum
+	bgeu	s0, t3, .Lwfi
+
 	LADDR	t0, _Per_CPU_Information
 	slli	t1, s0, PER_CPU_CONTROL_SIZE_LOG2
 	add	s1, t0, t1
@@ -100,6 +109,9 @@ SYM(_start):
 	tail	boot_card
 
 #ifdef RTEMS_SMP
+.Lwfi:
+	wfi
+	j	.Lwfi
 
 .Lstart_on_secondary_processor: