Re: [PATCH 4/5] x86/xen: Don't register Xen IPIs when they aren't going to be used

[boris.ostrovsky@xxxxxxxxxx]

On 12/24/20 6:53 AM, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> In the case where xen_have_vector_callback is false, we still register
> the IPI vectors in xen_smp_intr_init() for the secondary CPUs even
> though they aren't going to be used. Stop doing that.
>
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
>  arch/x86/xen/enlighten_hvm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
> index a1c07e0c888e..7a6ef517e81a 100644
> --- a/arch/x86/xen/enlighten_hvm.c
> +++ b/arch/x86/xen/enlighten_hvm.c
> @@ -164,10 +164,10 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
>       else
>               per_cpu(xen_vcpu_id, cpu) = cpu;
>       rc = xen_vcpu_setup(cpu);


Without vector callback we will not be calling xen_vcpu_setup(0) so why should 
we still call it here for APs?


-boris


> -     if (rc)
> +     if (rc || !xen_have_vector_callback)
>               return rc;
>  
> -     if (xen_have_vector_callback && xen_feature(XENFEAT_hvm_safe_pvclock))
> +     if (xen_feature(XENFEAT_hvm_safe_pvclock))
>               xen_setup_timer(cpu);
>  
>       rc = xen_smp_intr_init(cpu);