Re: [PATCH v1 13/15] xen/riscv: implement reprogram_timer() using SBI

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.12.2025 18:03, Oleksii Kurochko wrote:
> @@ -39,6 +43,33 @@ static void __init preinit_dt_xen_time(void)
>      cpu_khz = rate / 1000;
>  }
>  
> +int reprogram_timer(s_time_t timeout)
> +{
> +    uint64_t deadline, now;
> +    int rc;
> +
> +    if ( timeout == 0 )
> +    {
> +        /* Disable timers */
> +        csr_clear(CSR_SIE, BIT(IRQ_S_TIMER, UL));
> +
> +        return 1;
> +    }
> +
> +    deadline = ns_to_ticks(timeout) + boot_clock_cycles;
> +    now = get_cycles();
> +    if ( deadline <= now )
> +        return 0;
> +
> +    /* Enable timer */
> +    csr_set(CSR_SIE, BIT(IRQ_S_TIMER, UL));

Still learning RISC-V, so question for my understanding: Even if the timeout
is short enough to expire before the one SIE bit will be set, the interrupt
will still occur (effectively immediately)? (Else the bit may need setting
first.)

> +    if ( (rc = sbi_set_timer(deadline)) )
> +        panic("%s: timer wasn't set because: %d\n", __func__, rc);

Hmm, if this function ends up being used from any guest accessible path (e.g.
a hypercall), such panic()-ing better shouldn't be there.

> +    return 1;
> +}

Finally, before we get yet another instance of this de-fact boolean function:
Wouldn't we better globally switch it to be properly "bool" first?

Jan