On 11.02.2026 16:12, Jan Beulich wrote: > On 09.02.2026 17:52, Oleksii Kurochko wrote: >> Implement reprogram_timer() on RISC-V using the standard SBI timer call. >> >> The privileged architecture only defines machine-mode timer interrupts >> (using mtime/mtimecmp). Therefore, timer services for S/HS/VS mode must >> be provided by M-mode via SBI calls. SSTC (Supervisor-mode Timer Control) >> is optional and is not supported on the boards available to me, so the >> only viable approach today is to program the timer through SBI. >> >> reprogram_timer() enables/disables the supervisor timer interrupt and >> programs the next timer deadline using sbi_set_timer(). If the SBI call >> fails, the code panics, because sbi_set_timer() is expected to return >> either 0 or -ENOSUPP (this has been stable from early OpenSBI versions to >> the latest ones). The SBI spec does not define a standard negative error >> code for this call, and without SSTC there is no alternative method to >> program the timer, so the SBI timer call must be available. >> >> reprogram_timer() currently returns int for compatibility with the >> existing prototype. While it might be cleaner to return bool, keeping the >> existing signature avoids premature changes in case sbi_set_timer() ever >> needs to return other values (based on which we could try to avoid >> panic-ing) in the future. >> >> Signed-off-by: Oleksii Kurochko <[email protected]> > > Acked-by: Jan Beulich <[email protected]> > >> --- >> Changes in v3: >> - Correct the comments in reprogram_timer(). >> - Move enablement of timer interrupt after sbi_set_timer() to avoid >> potentially receiving a timer interrupt between these 2 operations. > > I'd like to mention that this is of only hypothetical concern, at least for > the sole caller in common code: That's doing the call with IRQs off, so > only the bit in SIP could become set too early, while no IRQ would surface > before timer_softirq_action() turns IRQs on again.
Actually, further to this: If IRQs were on, an IRQ could still surface between the two operations, when the SIE bit was already sent upon entry into the function (i.e. for example when a timeout is being moved earlier). Jan
