block/raw-win32: implement .bdrv_detach/attach_aio_context()

Drop the assumption that we're using the main AioContext for raw-win32.
Convert the aio-win32 code to support detach/attach and replace
qemu_aio_wait() with aio_poll().

The .bdrv_detach/attach_aio_context() interfaces move the aio-win32
event notifier from the old to the new AioContext.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/raw-aio.h

@@ -51,6 +51,10 @@ BlockDriverAIOCB *win32_aio_submit(BlockDriverState *bs,
         QEMUWin32AIOState *aio, HANDLE hfile,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockDriverCompletionFunc *cb, void *opaque, int type);
+void win32_aio_detach_aio_context(QEMUWin32AIOState *aio,
+                                  AioContext *old_context);
+void win32_aio_attach_aio_context(QEMUWin32AIOState *aio,
+                                  AioContext *new_context);
 #endif
 
 #endif /* QEMU_RAW_AIO_H */

block/raw-win32.c

@@ -200,6 +200,25 @@ static int set_sparse(int fd)
 				 NULL, 0, NULL, 0, &returned, NULL);
 }
 
+static void raw_detach_aio_context(BlockDriverState *bs)
+{
+    BDRVRawState *s = bs->opaque;
+
+    if (s->aio) {
+        win32_aio_detach_aio_context(s->aio, bdrv_get_aio_context(bs));
+    }
+}
+
+static void raw_attach_aio_context(BlockDriverState *bs,
+                                   AioContext *new_context)
+{
+    BDRVRawState *s = bs->opaque;
+
+    if (s->aio) {
+        win32_aio_attach_aio_context(s->aio, new_context);
+    }
+}
+
 static void raw_probe_alignment(BlockDriverState *bs)
 {
     BDRVRawState *s = bs->opaque;
@@ -339,6 +358,8 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags,
             error_setg_errno(errp, -ret, "Could not enable AIO");
             goto fail;
         }
+
+        win32_aio_attach_aio_context(s->aio, bdrv_get_aio_context(bs));
     }
 
     raw_probe_alignment(bs);
@@ -388,6 +409,7 @@ static void raw_close(BlockDriverState *bs)
     BDRVRawState *s = bs->opaque;
 
     if (s->aio) {
+        win32_aio_detach_aio_context(s->aio, bdrv_get_aio_context(bs));
         win32_aio_cleanup(s->aio);
         s->aio = NULL;
     }
@@ -687,6 +709,9 @@ static BlockDriver bdrv_host_device = {
     .bdrv_aio_writev    = raw_aio_writev,
     .bdrv_aio_flush     = raw_aio_flush,
 
+    .bdrv_detach_aio_context = raw_detach_aio_context,
+    .bdrv_attach_aio_context = raw_attach_aio_context,
+
     .bdrv_getlength      = raw_getlength,
     .has_variable_length = true,
 

block/win32-aio.c

@@ -40,6 +40,7 @@ struct QEMUWin32AIOState {
     HANDLE hIOCP;
     EventNotifier e;
     int count;
+    bool is_aio_context_attached;
 };
 
 typedef struct QEMUWin32AIOCB {
@@ -114,7 +115,7 @@ static void win32_aio_cancel(BlockDriverAIOCB *blockacb)
      * wait for completion.
      */
     while (!HasOverlappedIoCompleted(&waiocb->ov)) {
-        qemu_aio_wait();
+        aio_poll(bdrv_get_aio_context(blockacb->bs), true);
     }
 }
 
@@ -180,6 +181,20 @@ int win32_aio_attach(QEMUWin32AIOState *aio, HANDLE hfile)
     }
 }
 
+void win32_aio_detach_aio_context(QEMUWin32AIOState *aio,
+                                  AioContext *old_context)
+{
+    aio_set_event_notifier(old_context, &aio->e, NULL);
+    aio->is_aio_context_attached = false;
+}
+
+void win32_aio_attach_aio_context(QEMUWin32AIOState *aio,
+                                  AioContext *new_context)
+{
+    aio->is_aio_context_attached = true;
+    aio_set_event_notifier(new_context, &aio->e, win32_aio_completion_cb);
+}
+
 QEMUWin32AIOState *win32_aio_init(void)
 {
     QEMUWin32AIOState *s;
@@ -194,8 +209,6 @@ QEMUWin32AIOState *win32_aio_init(void)
         goto out_close_efd;
     }
 
-    qemu_aio_set_event_notifier(&s->e, win32_aio_completion_cb);
-
     return s;
 
 out_close_efd:
@@ -207,7 +220,7 @@ QEMUWin32AIOState *win32_aio_init(void)
 
 void win32_aio_cleanup(QEMUWin32AIOState *aio)
 {
-    qemu_aio_set_event_notifier(&aio->e, NULL);
+    assert(!aio->is_aio_context_attached);
     CloseHandle(aio->hIOCP);
     event_notifier_cleanup(&aio->e);
     g_free(aio);