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Re: [XEN PATCH v3 12/16] x86/vmx: guard access to cpu_has_vmx_* in common code


  • To: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 10 Jun 2024 17:16:28 +0200
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  • Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Xenia Ragiadakou <xenia.ragiadakou@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 10 Jun 2024 15:16:37 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 03.06.2024 13:30, Sergiy Kibrik wrote:
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -5197,7 +5197,7 @@ int hvm_debug_op(struct vcpu *v, int32_t op)
>      {
>          case XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_ON:
>          case XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_OFF:
> -            if ( !cpu_has_monitor_trap_flag )
> +            if ( !using_vmx || !cpu_has_monitor_trap_flag )
>                  return -EOPNOTSUPP;
>              break;

Here and elsewhere you're adding a redundant check of cpu_has_vmx, even
if that's not visible without looking at using_vmx. I'm inclined to
think that adding IS_ENABLED() to the various cpu_has_* that you care
about might end up better (for being a little cheaper at runtime).

Jan



 


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