[PATCH v8 03/22] riscv: Enable interrupts during syscalls with M-Mode

[Palmer Dabbelt]

On Thu, 10 Dec 2020 06:02:54 PST (-0800), Damien Le Moal wrote:
> When running is M-Mode (no MMU config), MPIE does not get set. This
> results in all syscalls being executed with interrupts disabled as
> handle_exception never sets SR_IE as it always sees SR_PIE being
> cleared. Fix this by always force enabling interrupts in
> handle_syscall when CONFIG_RISCV_M_MODE is enabled.
>
> Signed-off-by: Damien Le Moal <damien.lemoal at wdc.com>
> ---
>  arch/riscv/kernel/entry.S | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 524d918f3601..080eb8d78589 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -155,6 +155,15 @@ skip_context_tracking:
>  	tail do_trap_unknown
>
>  handle_syscall:
> +#ifdef CONFIG_RISCV_M_MODE
> +	/*
> +	 * When running is M-Mode (no MMU config), MPIE does not get set.
> +	 * As a result, we need to force enable interrupts here because
> +	 * handle_exception did not do set SR_IE as it always sees SR_PIE
> +	 * being cleared.
> +	 */
> +	csrs CSR_STATUS, SR_IE
> +#endif
>  #if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
>  	/* Recover a0 - a7 for system calls */
>  	REG_L a0, PT_A0(sp)

Reviewed-by: Palmer Dabbelt <palmerdabbelt at google.com>