Re: [Xen-devel] [RFC PATCH V2 08/14] Define N-level event channel registration interface

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.01.13 at 15:30, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> @@ -258,6 +259,38 @@ struct evtchn_reset {
>  typedef struct evtchn_reset evtchn_reset_t;
>  
>  /*
> + * EVTCHNOP_register_nlevel: Register N-level event channel
> + * NOTES:
> + *  1. Currently only 3-level is supported.
> + *  2. Should fall back to 2-level if this call fails.
> + */
> +/* 64 bit guests need 8 pages for evtchn_pending and evtchn_mask for
> + * 256k event channels while 32 bit ones only need 1 page for 32k
> + * event channels. */
> +#define EVTCHN_MAX_L3_PAGES 8
> +struct evtchn_register_3level {
> +    /* IN parameters. */
> +    uint32_t nr_pages;
> +    XEN_GUEST_HANDLE(xen_pfn_t) evtchn_pending;
> +    XEN_GUEST_HANDLE(xen_pfn_t) evtchn_mask;
> +    uint32_t nr_vcpus;

Any reason not to put this adjacent to the other uint32_t?

> +    XEN_GUEST_HANDLE(xen_pfn_t) l2sel_mfns;
> +    XEN_GUEST_HANDLE(xen_pfn_t) l2sel_offsets;
> +};
> +typedef struct evtchn_register_3level evtchn_register_3level_t;
> +DEFINE_XEN_GUEST_HANDLE(evtchn_register_3level_t);
> +
> +struct evtchn_register_nlevel {
> +    /* IN parameters. */
> +    uint32_t level;
> +    union {
> +        XEN_GUEST_HANDLE(evtchn_register_3level_t) l3;

Do you really need the extra level of indirection here (i.e. can't
you embed the structure rather than having a handle to it)?

> +    } u;
> +};
> +typedef struct evtchn_register_nlevel evtchn_register_nlevel_t;
> +DEFINE_XEN_GUEST_HANDLE(evtchn_register_nlevel_t);
> +
> +/*
>   * ` enum neg_errnoval
>   * ` HYPERVISOR_event_channel_op_compat(struct evtchn_op *op)
>   * `

Jan


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