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-- 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>
---
drivers/xen/grant-table.c | 74 +++++++++++++++++++++++++++++++++++++++++++++
include/xen/grant_table.h | 13 ++++++++
2 files changed, 87 insertions(+), 0 deletions(-)

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index bd325fd..4a10e3f 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -120,6 +120,16 @@ struct gnttab_ops {
* by bit operations.
*/
int (*query_foreign_access)(grant_ref_t);
+ /*
+ * Grant a domain to access a range of bytes within the page referred by
+ * an available grant entry. First parameter is grant entry reference
+ * number, second one is id of grantee domain, third one is frame
+ * address of subpage grant, forth one is grant type and flag
+ * information, fifth one is offset of the range of bytes, and last one
+ * is length of bytes to be accessed.
+ */
+ void (*update_subpage_entry)(grant_ref_t, domid_t, unsigned long, int,
+ unsigned, unsigned);
};

static struct gnttab_ops *gnttab_interface;
@@ -261,6 +271,69 @@ 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;
+
+ if (flags & (GTF_accept_transfer | GTF_reading |
+ GTF_writing | GTF_transitive))
+ return -EPERM;
+
+ if (gnttab_interface->update_subpage_entry == NULL)
+ return -ENOSYS;
+
+ ref = get_free_entries(1);
+ if (unlikely(ref < 0))
+ return -ENOSPC;
+
+ gnttab_interface->update_subpage_entry(ref, domid, frame, flags,
+ page_off, length);
+
+ 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 +886,7 @@ 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)
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index fea4954..2b492b9 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -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);
--
1.7.6.4


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