Re: [PATCH 2/6] gnttab: allow per-domain control over transitive grants

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 17/09/2021 16:46, Roger Pau Monne wrote:
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 7f8456c50e..fe2201fca1 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -96,6 +96,14 @@ struct xen_domctl_createdomain {
>      int32_t max_maptrack_frames;
>      int32_t max_grant_version;
>  
> +/* Allow transitive grants. */
> +#define _XEN_DOMCTL_GRANT_transitive  0
> +#define XEN_DOMCTL_GRANT_transitive   (1U << _XEN_DOMCTL_GRANT_transitive)

There's no need for bit position variables.

> +
> +#define XEN_DOMCTL_GRANT_MAX XEN_DOMCTL_GRANT_transitive
> +
> +    uint32_t grant_opts;

So far, we've got 3 bits of information, v1, v2 and transitive, and
we're tight on space in the structure with loads more to fit in.

I was thinking grant_flags or equiv to contain these 3 settings, and any
further which might appear.


One thing which is missing however is the enumeration of which settings
are available, and rejection of bad settings.  If v2 is disabled
globally, trying to create a VM with v2 needs to fail.

~Andrew