Re: [PATCH 1/2] xen/granttable: Support sub-page grants

[ANNIE LI <annie.li@oracle.com>]

> +void gnttab_grant_foreign_access_ref_subpage_v2(grant_ref_t ref, domid_t domid,
> +						unsigned long frame, int flags,
> +						unsigned page_off,
> +						unsigned length)
> +{
> +	BUG_ON(flags&  (GTF_accept_transfer | GTF_reading |
> +			GTF_writing | GTF_transitive));
This is slightly changed from the initial code, welcome your suggestions.

Initial condition is:
BUG_ON(flags & (GTF_accept_transfer | GTF_reading | GTF_writing | 
GTF_sub_page | GTF_permit_access));

GTF_sub_page | GTF_permit_access will be set later in this function, so 
it is necessary to verify this flag here.
GTF_transitive and GTF_sub_page can not be enabled at same time, so 
GTF_transitive is checked here to avoid those two flags are both enabled.

Same code was changed in corresponding transitive function.

Thanks
Annie
> +	BUG_ON(grant_table_version == 1);
> +	gnttab_shared.v2[ref].sub_page.frame = frame;
> +	gnttab_shared.v2[ref].sub_page.page_off = page_off;
> +	gnttab_shared.v2[ref].sub_page.length = length;
> +	gnttab_shared.v2[ref].hdr.domid = domid;
> +	wmb();
> +	gnttab_shared.v2[ref].hdr.flags =
> +				GTF_permit_access | GTF_sub_page | flags;
> +}
>