Re: [PATCH v4 08/16] xen/riscv: introduce basic vtimer infrastructure for guests

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 2/17/26 3:59 PM, Jan Beulich wrote:
> On 13.02.2026 17:28, Oleksii Kurochko wrote:
> > Lay the groundwork for guest timer support by introducing a per-vCPU
> > virtual timer backed by Xen’s common timer infrastructure.
> >
> > The virtual timer is programmed in response to the guest SBI
> > sbi_set_timer() call and injects a virtual supervisor timer interrupt
> > into the vCPU when it expires.
> >
> > While a dedicated struct vtimer is not strictly required at present,
> > it is expected to become necessary once SSTC support is introduced.
> > In particular, it will need to carry additional state such as whether
> > SSTC is enabled, the next compare value (e.g. for the VSTIMECMP CSR)
> > to be saved and restored across context switches, and time delta state
> > (e.g. HTIMEDELTA) required for use cases such as migration. Introducing
> > struct vtimer now avoids a later refactoring.
> >
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
> with a question and a remark.
>
> > @@ -126,6 +130,8 @@ int arch_vcpu_create(struct vcpu *v)
> >   
> >   void arch_vcpu_destroy(struct vcpu *v)
> >   {
> > +    vcpu_timer_destroy(v);
> It feels pretty late to do this, yet I notice vcpu_teardown() doesn't invoke
> any per-arch function (yet). There's arch_domain_teardown(), though, which
> technically could do this for all vCPU-s in a domain.
Why it isn't enough to be implicitly called by domain_destroy()?

> > --- /dev/null
> > +++ b/xen/arch/riscv/include/asm/vtimer.h
> > @@ -0,0 +1,20 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * (c) 2023-2024 Vates
> > + */
> Is this correct? Is this needed here?
I'll just drop that to be aligned with other headers.

~ Oleksii