Re: [PATCH v2 12/16] xen/riscv: introduce sbi_set_timer()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.01.2026 17:47, Oleksii Kurochko wrote:
> --- a/xen/arch/riscv/include/asm/sbi.h
> +++ b/xen/arch/riscv/include/asm/sbi.h
> @@ -29,6 +29,10 @@
>  
>  #define SBI_EXT_BASE                    0x10
>  #define SBI_EXT_RFENCE                  0x52464E43
> +#define SBI_EXT_TIME                    0x54494D45
> +
> +/* SBI function IDs for TIME extension */
> +#define SBI_EXT_TIME_SET_TIMER          0x0

Nit: Do you really mean to have the time extension IDs above ...

>  /* SBI function IDs for BASE extension */
>  #define SBI_EXT_BASE_GET_SPEC_VERSION   0x0

... the base extension ones?

> @@ -134,6 +138,20 @@ int sbi_remote_hfence_gvma(const cpumask_t *cpu_mask, 
> vaddr_t start,
>  int sbi_remote_hfence_gvma_vmid(const cpumask_t *cpu_mask, vaddr_t start,
>                                  size_t size, unsigned long vmid);
>  
> +/*
> + * Programs the clock for next event after stime_value time. This function 
> also
> + * clears the pending timer interrupt bit.
> + * If the supervisor wishes to clear the timer interrupt without scheduling 
> the
> + * next timer event, it can either request a timer interrupt infinitely far
> + * into the future (i.e., (uint64_t)-1), or it can instead mask the timer
> + * interrupt by clearing sie.STIE CSR bit.
> + * The stime_value parameter represents absolute time measured in ticks.
> + *
> + * This SBI call returns 0 upon success or an implementation specific 
> negative
> + * error code.
> + */
> +extern int (*sbi_set_timer)(uint64_t stime_value);

__read_mostly or even __ro_after_init?

> @@ -326,6 +358,14 @@ int __init sbi_init(void)
>              sbi_rfence = sbi_rfence_v02;
>              printk("SBI v0.2 RFENCE extension detected\n");
>          }
> +
> +        if ( sbi_probe_extension(SBI_EXT_TIME) > 0 )
> +        {
> +            sbi_set_timer = sbi_set_timer_v02;
> +            printk("SBI v0.2 TIME extension detected\n");

Is this really relevant to log especially in release builds? IOW can this at
least be downgraded to dprintk()?

Jan