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: Annie Li <annie.li@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 1589ea1..c8312c7 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -120,6 +120,17 @@
* 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 @@
}
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 @@
.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)