Re: [Xen-devel] [PATCHv1 6/6] evtchn: pad struct evtchn to 64 bytes

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.06.15 at 16:59, <david.vrabel@xxxxxxxxxx> wrote:
> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -110,8 +110,8 @@ struct evtchn
>      u8 priority;
>      u8 last_priority;
>      u16 last_vcpu_id;
> -#ifdef XSM_ENABLE
>      union {
> +#ifdef XSM_ENABLE
>  #ifdef XSM_NEED_GENERIC_EVTCHN_SSID
>          /*
>           * If an XSM module needs more space for its event channel context,
> @@ -127,8 +127,9 @@ struct evtchn
>           */
>          u32 flask_sid;
>  #endif
> -    } ssid;
>  #endif
> +        u8 __pad[24]; /* Round size to power of two. */

The union in the middle differing in size between 32- and 64-bit
architectures, can this really be a uniform value? Wouldn't it be
better to simply mark the whole structured aligned(64)?

Also I don't see the need for an underscore here, not to speak of
even two of them.

Jan


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