xen/gntalloc,gntdev: Add unmap notify ioctl

This ioctl allows the users of a shared page to be notified when
the other end exits abnormally.

[v2: updated description in structs]
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/include/xen/gntalloc.h b/include/xen/gntalloc.h
index bc3b85e8bff7..76bd58065f4f 100644
--- a/include/xen/gntalloc.h
+++ b/include/xen/gntalloc.h
@@ -47,4 +47,36 @@ struct ioctl_gntalloc_dealloc_gref {
         /* Number of references to unmap */
         uint32_t count;
 };
+
+/*
+ * Sets up an unmap notification within the page, so that the other side can do
+ * cleanup if this side crashes. Required to implement cross-domain robust
+ * mutexes or close notification on communication channels.
+ *
+ * Each mapped page only supports one notification; multiple calls referring to
+ * the same page overwrite the previous notification. You must clear the
+ * notification prior to the IOCTL_GNTALLOC_DEALLOC_GREF if you do not want it
+ * to occur.
+ */
+#define IOCTL_GNTALLOC_SET_UNMAP_NOTIFY \
+_IOC(_IOC_NONE, 'G', 7, sizeof(struct ioctl_gntalloc_unmap_notify))
+struct ioctl_gntalloc_unmap_notify {
+        /* IN parameters */
+        /* Offset in the file descriptor for a byte within the page (same as
+         * used in mmap). If using UNMAP_NOTIFY_CLEAR_BYTE, this is the byte to
+         * be cleared. Otherwise, it can be any byte in the page whose
+         * notification we are adjusting.
+         */
+        uint64_t index;
+        /* Action(s) to take on unmap */
+        uint32_t action;
+        /* Event channel to notify */
+        uint32_t event_channel_port;
+};
+
+/* Clear (set to zero) the byte specified by index */
+#define UNMAP_NOTIFY_CLEAR_BYTE 0x1
+/* Send an interrupt on the indicated event channel */
+#define UNMAP_NOTIFY_SEND_EVENT 0x2
+
 #endif /* __LINUX_PUBLIC_GNTALLOC_H__ */