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

[Jan Beulich <jbeulich@xxxxxxxx>]

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.

Jan