Re: [PATCH v3 12/16] xen/riscv: introduce sbi_set_timer()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.02.2026 17:52, Oleksii Kurochko wrote:
> Introduce a function pointer for sbi_set_timer(), since different OpenSBI
> versions may implement the TIME extension with different extension IDs
> and/or function IDs.
> 
> If the TIME extension is not available, fall back to the legacy timer
> mechanism. This is useful when Xen runs as a guest under another Xen,
> because the TIME extension is not currently virtualised and therefore
> will not appear as available.
> Despite of the fact that sbi_set_timer_v01 is introduced and used as
> fall back, SBI v0.1 still isn't fully supported (with the current SBI
> calls usage, sbi_rfence_v01 should be introduced too), so panic()
> in sbi_init() isn't removed.
> 
> The sbi_set_timer() pointer will be used by reprogram_timer() to program
> Xen’s physical timer as without SSTC extension there is no any other
> option except SBI call to do that as only M-timer is available for us.
> 
> Use dprintk() for all the cases to print that a speicifc SBI extension
> is available as it isn't really necessary in case of release builds.
> 
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
with one further request:

> @@ -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.

"after stime_value time" reads as if this was a relative input, stime_value 
units
of time need to pass until the event. Iirc values passed are absolute, though.
Furthermore it was my understanding that the interrupt being raised is dependent
upon clock >= value, not clock > value (where the latter is what "after" means
when taken to apply to an absolute value).

Jan