Re: [Xen-devel] [PATCH v4 11/34] xsplice: Design document

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

> diff --git a/docs/misc/xsplice.markdown b/docs/misc/xsplice.markdown
> index 6aa5a27..8252e6c 100644
> --- a/docs/misc/xsplice.markdown
> +++ b/docs/misc/xsplice.markdown
> @@ -487,7 +487,9 @@ hypervisor.
>  The caller provides:
>  
>   * `version`. Initially (on first hypercall) *MUST* be zero.
> - * `idx` index iterator. On first call *MUST* be zero, subsequent calls 
> varies.
> + * `idx` index iterator. The index into the hypervisor's payload count. It is
> +    recommended that on first invocation zero be used so that `nr` (which the
> +    hypervisor will update with the remaining payload count) be provided.
>   * `nr` the max number of entries to populate.
>   * `pad` - *MUST* be zero.
>   * `status` virtual address of where to write `struct xen_xsplice_status`
> @@ -538,9 +540,9 @@ struct xen_sysctl_xsplice_list {
>                                                 On subsequent calls reuse 
> value.  
>                                                 If varies between calls, we 
> are  
>                                               * getting stale data. */  
> -    uint32_t idx;                           /* IN/OUT: Index into array. */  
> +    uint32_t idx;                           /* IN: Index into array. */  
>      uint32_t nr;                            /* IN: How many status, names, 
> and len  
> -                                               should fill out.  
> +                                               should be filled out.  
>                                                 OUT: How many payloads left. 
> */  
>      uint32_t pad;                           /* IN: Must be zero. */  
>      XEN_GUEST_HANDLE_64(xen_xsplice_status_t) status;  /* OUT. Must have 
> enough  
> > 
> > Jan
> > 

And it occurred to me that we can do a probe call similar to XEN_VERSION.

That is fill 'nr' with zero and ->names, ->status, ->list, etc can be NULL.
Then 'nr' will be filled back with the number of payloads.

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