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Commit 6666754b authored by Annie Li's avatar Annie Li Committed by Konrad Rzeszutek Wilk
Browse files

xen/granttable: Support sub-page grants 



- They can't be used to map the page (so can only be used in a GNTTABOP_copy
  hypercall).
- It's possible to grant access with a finer granularity than whole pages.
- Xen guarantees that they can be revoked quickly (a normal map grant can
  only be revoked with the cooperation of the domain which has been granted
  access).

Signed-off-by: default avatarAnnie Li <annie.li@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 9dbc71d5

drivers/xen/grant-table.c

+72 −0
Original line number Diff line number Diff line
@@ -120,6 +120,17 @@ struct gnttab_ops { 
	 * by bit operations.

	 */

	int (*query_foreign_access)(grant_ref_t ref);

	/*

	 * Grant a domain to access a range of bytes within the page referred by

	 * an available grant entry. Ref parameter is reference of a grant entry

	 * which will be sub-page accessed, domid is id of grantee domain, frame

	 * is frame address of subpage grant, flags is grant type and flag

	 * information, page_off is offset of the range of bytes, and length is

	 * length of bytes to be accessed.

	 */

	void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,

				     unsigned long frame, int flags,

				     unsigned page_off, unsigned length);

};



static struct gnttab_ops *gnttab_interface;
@@ -261,6 +272,66 @@ int gnttab_grant_foreign_access(domid_t domid, unsigned long frame, 
}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);



void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,

				    unsigned long frame, int flags,

				    unsigned page_off,

				    unsigned length)

{

	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;

}



int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,

					    unsigned long frame, int flags,

					    unsigned page_off,

					    unsigned length)

{

	if (flags & (GTF_accept_transfer | GTF_reading |

		     GTF_writing | GTF_transitive))

		return -EPERM;



	if (gnttab_interface->update_subpage_entry == NULL)

		return -ENOSYS;



	gnttab_interface->update_subpage_entry(ref, domid, frame, flags,

					       page_off, length);



	return 0;

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);



int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,

					int flags, unsigned page_off,

					unsigned length)

{

	int ref, rc;



	ref = get_free_entries(1);

	if (unlikely(ref < 0))

		return -ENOSPC;



	rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags,

						     page_off, length);

	if (rc < 0) {

		put_free_entry(ref);

		return rc;

	}



	return ref;

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);



bool gnttab_subpage_grants_available(void)

{

	return gnttab_interface->update_subpage_entry != NULL;

}

EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);



static int gnttab_query_foreign_access_v1(grant_ref_t ref)

{

	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
@@ -813,6 +884,7 @@ static struct gnttab_ops gnttab_v2_ops = { 
	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,

	.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,

};



static void gnttab_request_version(void)

include/xen/grant_table.h

+13 −0
Original line number Diff line number Diff line
@@ -62,6 +62,15 @@ int gnttab_resume(void); 


int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,

				int readonly);

int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,

					int flags, unsigned page_off,

					unsigned length);



/*

 * Are sub-page grants available on this version of Xen?  Returns true if they

 * are, and false if they're not.

 */

bool gnttab_subpage_grants_available(void);



/*

 * End access through the given grant reference, iff the grant entry is no
@@ -108,6 +117,10 @@ void gnttab_cancel_free_callback(struct gnttab_free_callback *callback); 


void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,

				     unsigned long frame, int readonly);

int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,

					    unsigned long frame, int flags,

					    unsigned page_off,

					    unsigned length);



void gnttab_grant_foreign_transfer_ref(grant_ref_t, domid_t domid,

				       unsigned long pfn);