Re: [PATCH v2] domain: skip more stuff for idle's vCPU-s in vcpu_create()

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Feb 16, 2026 at 04:54:30PM +0100, Jan Beulich wrote:
> Nothing hypercall-related needs setting up there. Nor do we need to
> check whether the idle domain is shutting down - it never will.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

> ---
> v2: Drop vmtrace_alloc_buffer() part.
> 
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -475,12 +475,6 @@ struct vcpu *vcpu_create(struct domain *
>      v->vcpu_id = vcpu_id;
>      v->dirty_cpu = VCPU_CPU_CLEAN;
>  
> -    rwlock_init(&v->virq_lock);
> -
> -    tasklet_init(&v->continue_hypercall_tasklet, NULL, NULL);
> -
> -    grant_table_init_vcpu(v);
> -
>      if ( is_idle_domain(d) )
>      {
>          v->runstate.state = RUNSTATE_running;
> @@ -488,6 +482,12 @@ struct vcpu *vcpu_create(struct domain *
>      }
>      else
>      {
> +        rwlock_init(&v->virq_lock);
> +
> +        tasklet_init(&v->continue_hypercall_tasklet, NULL, NULL);
> +
> +        grant_table_init_vcpu(v);
> +
>          v->runstate.state = RUNSTATE_offline;
>          v->runstate.state_entry_time = NOW();
>          set_bit(_VPF_down, &v->pause_flags);
> @@ -516,7 +516,8 @@ struct vcpu *vcpu_create(struct domain *
>      }
>  
>      /* Must be called after making new vcpu visible to for_each_vcpu(). */
> -    vcpu_check_shutdown(v);
> +    if ( !is_idle_domain(d) )
> +        vcpu_check_shutdown(v);

I would possibly leave this as-is.  I agree that the idle domain will
never shut down, but it's possibly best to needlessly call into
vcpu_check_shutdown() for the idle domain rather than adding the extra
conditional for the common case?

My Ack stands regardless.

Thanks, Roger.