[PATCH] riscv: Fix local irq restore when flags indicates irq disabled

[Palmer Dabbelt]

On Tue, 25 Jul 2023 00:05:49 PDT (-0700), luxu.kernel at bytedance.com wrote:
> When arch_local_irq_restore() is called with flags indicating irqs
> disabled, we need to clear SR_IE bit in CSR_STATUS, whereas current
> implementation based on csr_set() function only sets SR_IE bit of
> CSR_STATUS when SR_IE bit of flags is high and does nothing when
> SR_IE bit of flags is low.
>
> This commit supplies csr clear operation when calling irq restore
> function with flags indicating irq disabled.
>
> Fixes: 6d60b6ee0c97 ("RISC-V: Device, timer, IRQs, and the SBI")
> Signed-off-by: Xu Lu <luxu.kernel at bytedance.com>
> ---
>  arch/riscv/include/asm/irqflags.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/irqflags.h b/arch/riscv/include/asm/irqflags.h
> index 08d4d6a5b7e9..7c31fc3c3559 100644
> --- a/arch/riscv/include/asm/irqflags.h
> +++ b/arch/riscv/include/asm/irqflags.h
> @@ -49,7 +49,10 @@ static inline int arch_irqs_disabled(void)
>  /* set interrupt enabled status */
>  static inline void arch_local_irq_restore(unsigned long flags)
>  {
> -	csr_set(CSR_STATUS, flags & SR_IE);
> +	if (flags & SR_IE)
> +		csr_set(CSR_STATUS, SR_IE);
> +	else
> +		csr_clear(CSR_STATUS, SR_IE);

Unless I'm missing something, the original version is correct: 
local_irq_restore() must be paired with a local_irq_save(), so we can 
only get here with interrupts disabled.

>  }
>
>  #endif /* _ASM_RISCV_IRQFLAGS_H */