Re: [PATCH v2 09/16] xen/riscv: introduce vcpu_kick() implementation

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 2/9/26 10:51 AM, Jan Beulich wrote:
> On 09.02.2026 10:40, Oleksii Kurochko wrote:
> > On 2/9/26 10:07 AM, Jan Beulich wrote:
> > > On 06.02.2026 17:36, Oleksii Kurochko wrote:
> > > > On 1/22/26 5:47 PM, Oleksii Kurochko wrote:
> > > > > Add a RISC-V implementation of vcpu_kick(), which unblocks the target
> > > > > vCPU and sends an event check IPI if the vCPU was running on another
> > > > > processor. This mirrors the behavior of Arm and enables proper vCPU
> > > > > wakeup handling on RISC-V.
> > > > >
> > > > > Remove the stub implementation from stubs.c, as it is now provided by
> > > > > arch/riscv/domain.c.
> > > > >
> > > > > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> > > > > Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
> > > > > ---
> > > > > Changes in v2:
> > > > >     - Add Acked-by: Jan Beulich <jbeulich@xxxxxxxx>.
> > > > > ---
> > > > >     xen/arch/riscv/domain.c | 14 ++++++++++++++
> > > > >     xen/arch/riscv/stubs.c  |  5 -----
> > > > >     2 files changed, 14 insertions(+), 5 deletions(-)
> > > > >
> > > > > diff --git a/xen/arch/riscv/domain.c b/xen/arch/riscv/domain.c
> > > > > index e38c0db62cac..13ac384c4b76 100644
> > > > > --- a/xen/arch/riscv/domain.c
> > > > > +++ b/xen/arch/riscv/domain.c
> > > > > @@ -1,8 +1,10 @@
> > > > >     /* SPDX-License-Identifier: GPL-2.0-only */
> > > > >     
> > > > > +#include <xen/cpumask.h>
> > > > >     #include <xen/init.h>
> > > > >     #include <xen/mm.h>
> > > > >     #include <xen/sched.h>
> > > > > +#include <xen/smp.h>
> > > > >     #include <xen/vmap.h>
> > > > >     
> > > > >     #include <asm/bitops.h>
> > > > > @@ -240,3 +242,15 @@ void vcpu_sync_interrupts(struct vcpu *v)
> > > > >     #   error "Update vsieh"
> > > > >     #endif
> > > > >     }
> > > > > +
> > > > > +void vcpu_kick(struct vcpu *v)
> > > > > +{
> > > > > +    bool running = v->is_running;
> > > > > +
> > > > > +    vcpu_unblock(v);
> > > > > +    if ( running && v != current )
> > > > > +    {
> > > > > +        perfc_incr(vcpu_kick);
> > > > Because of this it is needed to introduce:
> > > >      PERFCOUNTER(vcpu_kick, "vcpu: notify other vcpu")
> > > > Otherwise randconfig build will fail when CONFIG_PERF_COUNTERS=y.
> > > >
> > > > I would like to ask if it would be okay to add it xen/include/xen/perfc_defn.h
> > > > just after PERFCOUNTER(need_flush_tlb_flush,...) or would it be better to have
> > > > it in arch specific perfc_defn.h?
> > > Arch-specific please - it's not used by x86 nor ppc.
> > Then I will do the following changes:
> >
> > diff --git a/xen/arch/riscv/include/asm/Makefile 
> > b/xen/arch/riscv/include/asm/Makefile
> > index 3824f31c395c..86c56251d5d7 100644
> > --- a/xen/arch/riscv/include/asm/Makefile
> > +++ b/xen/arch/riscv/include/asm/Makefile
> > @@ -7,7 +7,6 @@ generic-y += hypercall.h
> >    generic-y += iocap.h
> >    generic-y += irq-dt.h
> >    generic-y += percpu.h
> > -generic-y += perfc_defn.h
> >    generic-y += random.h
> >    generic-y += softirq.h
> >    generic-y += vm_event.h
> > diff --git a/xen/arch/riscv/include/asm/perfc_defn.h 
> > b/xen/arch/riscv/include/asm/perfc_defn.h
> > new file mode 100644
> > index 000000000000..4fc161f1abad
> > --- /dev/null
> > +++ b/xen/arch/riscv/include/asm/perfc_defn.h
> > @@ -0,0 +1,7 @@
> > +/* This file is intended to be included multiple times. */
> > +/*#ifndef __XEN_PERFC_DEFN_H__*/
> > +/*#define __XEN_PERFC_DEFN_H__*/
> > +
> > +PERFCOUNTER(vcpu_kick, "vcpu: notify other vcpu")
> > +
> > +/*#endif*/ /* __XEN_PERFC_DEFN_H__ */
> >
> > and add the following to commit message:
> >       Since vcpu_kick() calls perfc_incr(vcpu_kick), add perfcounter for
> >       vcpu_kick to handle the case when CONFIG_PERF_COUNTERS=y. Although
> >       CONFIG_PERF_COUNTERS is not enabled by default, it can be enabled,
> >       for example, by randconfig what will lead to CI build issues.
> >
> > Note that I keep __XEN_PERFC_DEFN_H__ as other archictectures use the same,
> > not something like ASM__<arch>__PERFC_DEFN_H.
> Please don't copy this mistake. I actually question the commented-out pre-
> processor directives altogether: Misra also has a rule against commented-
> out code (directive 4.4, which we didn't accept [yet], but which exists
> nevertheless). Yet at the very least what's commented out should not be
> obviously wrong.
Do I understand correctly that it would be acceptable to simply drop the
commented-out preprocessor directives and keep only /* This file is intended
to be included multiple times. */ ?

~ Oleksii