[PATCH 1/3] bsps/riscv: Make SMP start more robust

[Chris Johns]

On 16/3/2023 5:59 pm, Sebastian Huber wrote:
> In SMP configurations, check that we run on a configured processor.  If not,
> then there is not much what can be done since we do not have a stack available

.... not much that can be done .... ?

No comment on the actual patch as I do not know RISCV :)

Chris

> 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..42e4348cd0 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 what 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:
>