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Commit 9438ce9d authored by Annie Li's avatar Annie Li Committed by Konrad Rzeszutek Wilk
Browse files

xen/granttable: Support transitive grants 



These allow a domain A which has been granted access on a page of domain B's
memory to issue domain C with a copy-grant on the same page.  This is useful
e.g. for forwarding packets between domains.

Signed-off-by: default avatarAnnie Li <annie.li@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 6666754b

drivers/xen/grant-table.c

+70 −0
Original line number Diff line number Diff line
@@ -131,6 +131,18 @@ struct gnttab_ops { 
	void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,

				     unsigned long frame, int flags,

				     unsigned page_off, unsigned length);

	/*

	 * Redirect an available grant entry on domain A to another grant

	 * reference of domain B, then allow domain C to use grant reference

	 * of domain B transitively. Ref parameter is an available grant entry

	 * reference on domain A, domid is id of domain C which accesses grant

	 * entry transitively, flags is grant type and flag information,

	 * trans_domid is id of domain B whose grant entry is finally accessed

	 * transitively, trans_gref is grant entry transitive reference of

	 * domain B.

	 */

	void (*update_trans_entry)(grant_ref_t ref, domid_t domid, int flags,

				   domid_t trans_domid, grant_ref_t trans_gref);

};



static struct gnttab_ops *gnttab_interface;
@@ -332,6 +344,63 @@ bool gnttab_subpage_grants_available(void) 
}

EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);



void gnttab_update_trans_entry_v2(grant_ref_t ref, domid_t domid,

				  int flags, domid_t trans_domid,

				  grant_ref_t trans_gref)

{

	gnttab_shared.v2[ref].transitive.trans_domid = trans_domid;

	gnttab_shared.v2[ref].transitive.gref = trans_gref;

	gnttab_shared.v2[ref].hdr.domid = domid;

	wmb();

	gnttab_shared.v2[ref].hdr.flags =

				GTF_permit_access | GTF_transitive | flags;

}



int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,

					  int flags, domid_t trans_domid,

					  grant_ref_t trans_gref)

{

	if (flags & (GTF_accept_transfer | GTF_reading |

		     GTF_writing | GTF_sub_page))

		return -EPERM;



	if (gnttab_interface->update_trans_entry == NULL)

		return -ENOSYS;



	gnttab_interface->update_trans_entry(ref, domid, flags, trans_domid,

					     trans_gref);



	return 0;

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans_ref);



int gnttab_grant_foreign_access_trans(domid_t domid, int flags,

				      domid_t trans_domid,

				      grant_ref_t trans_gref)

{

	int ref, rc;



	ref = get_free_entries(1);

	if (unlikely(ref < 0))

		return -ENOSPC;



	rc = gnttab_grant_foreign_access_trans_ref(ref, domid, flags,

						   trans_domid, trans_gref);

	if (rc < 0) {

		put_free_entry(ref);

		return rc;

	}



	return ref;

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans);



bool gnttab_trans_grants_available(void)

{

	return gnttab_interface->update_trans_entry != NULL;

}

EXPORT_SYMBOL_GPL(gnttab_trans_grants_available);



static int gnttab_query_foreign_access_v1(grant_ref_t ref)

{

	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
@@ -885,6 +954,7 @@ static struct gnttab_ops gnttab_v2_ops = { 
	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,

	.query_foreign_access		= gnttab_query_foreign_access_v2,

	.update_subpage_entry		= gnttab_update_subpage_entry_v2,

	.update_trans_entry		= gnttab_update_trans_entry_v2,

};



static void gnttab_request_version(void)

include/xen/grant_table.h

+12 −0
Original line number Diff line number Diff line
@@ -65,6 +65,9 @@ int gnttab_grant_foreign_access(domid_t domid, unsigned long frame, 
int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,

					int flags, unsigned page_off,

					unsigned length);

int gnttab_grant_foreign_access_trans(domid_t domid, int flags,

				      domid_t trans_domid,

				      grant_ref_t trans_gref);



/*

 * Are sub-page grants available on this version of Xen?  Returns true if they
@@ -72,6 +75,12 @@ int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame, 
 */

bool gnttab_subpage_grants_available(void);



/*

 * Are transitive grants available on this version of Xen?  Returns true if they

 * are, and false if they're not.

 */

bool gnttab_trans_grants_available(void);



/*

 * End access through the given grant reference, iff the grant entry is no

 * longer in use.  Return 1 if the grant entry was freed, 0 if it is still in
@@ -121,6 +130,9 @@ int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid, 
					    unsigned long frame, int flags,

					    unsigned page_off,

					    unsigned length);

int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,

					  int flags, domid_t trans_domid,

					  grant_ref_t trans_gref);



void gnttab_grant_foreign_transfer_ref(grant_ref_t, domid_t domid,

				       unsigned long pfn);