postcopy: postcopy_notify_shared_wake

Add a hook to allow a client userfaultfd to be 'woken'
when a page arrives, and a walker that calls that
hook for relevant clients given a RAMBlock and offset.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
index fcd53b8..2c73d77 100644
--- a/migration/postcopy-ram.h
+++ b/migration/postcopy-ram.h
@@ -148,6 +148,10 @@ struct PostCopyFD;
 
 /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */
 typedef int (*pcfdhandler)(struct PostCopyFD *pcfd, void *ufd);
+/* Notification to wake, either on place or on reception of
+ * a fault on something that's already arrived (race)
+ */
+typedef int (*pcfdwake)(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t offset);
 
 struct PostCopyFD {
     int fd;
@@ -155,6 +159,8 @@ struct PostCopyFD {
     void *data;
     /* Handler to be called whenever we get a poll event */
     pcfdhandler handler;
+    /* Notification to wake shared client */
+    pcfdwake waker;
     /* A string to use in error messages */
     const char *idstr;
 };
@@ -164,6 +170,10 @@ struct PostCopyFD {
  */
 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
+/* Call each of the shared 'waker's registerd telling them of
+ * availability of a block.
+ */
+int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset);
 /* postcopy_wake_shared: Notify a client ufd that a page is available
  *
  * Returns 0 on success