[PATCH v4 1/5] extend libvhost to support IOThread and coroutine

[Coiby Xu]

Previously libvhost dispatch events in its own GMainContext. Now vhost-user
client's kick event can be dispatched in block device drive's AioContext
thus IOThread is supported. And also allow vu_message_read and
vu_kick_cb to be replaced so QEMU can run them as coroutines.

Signed-off-by: Coiby Xu <address@hidden>
---
 contrib/libvhost-user/libvhost-user.c | 54 ++++++++++++++++++++++++---
 contrib/libvhost-user/libvhost-user.h | 38 ++++++++++++++++++-
 2 files changed, 85 insertions(+), 7 deletions(-)

diff --git a/contrib/libvhost-user/libvhost-user.c 
b/contrib/libvhost-user/libvhost-user.c
index b89bf18501..f95664bb22 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -67,8 +67,6 @@
 /* The version of inflight buffer */
 #define INFLIGHT_VERSION 1
 
-#define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
-
 /* The version of the protocol we support */
 #define VHOST_USER_VERSION 1
 #define LIBVHOST_USER_DEBUG 0
@@ -260,7 +258,7 @@ have_userfault(void)
 }
 
 static bool
-vu_message_read(VuDev *dev, int conn_fd, VhostUserMsg *vmsg)
+vu_message_read_(VuDev *dev, int conn_fd, VhostUserMsg *vmsg)
 {
     char control[CMSG_SPACE(VHOST_MEMORY_MAX_NREGIONS * sizeof(int))] = { };
     struct iovec iov = {
@@ -328,6 +326,17 @@ fail:
     return false;
 }
 
+static bool vu_message_read(VuDev *dev, int conn_fd, VhostUserMsg *vmsg)
+{
+    vu_read_msg_cb read_msg;
+    if (dev->co_iface) {
+        read_msg = dev->co_iface->read_msg;
+    } else {
+        read_msg = vu_message_read_;
+    }
+    return read_msg(dev, conn_fd, vmsg);
+}
+
 static bool
 vu_message_write(VuDev *dev, int conn_fd, VhostUserMsg *vmsg)
 {
@@ -1075,9 +1084,14 @@ vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
     }
 
     if (dev->vq[index].kick_fd != -1 && dev->vq[index].handler) {
+        if (dev->set_watch_packed_data) {
+            dev->set_watch_packed_data(dev, dev->vq[index].kick_fd, 
VU_WATCH_IN,
+                                       dev->co_iface->kick_callback,
+                                       (void *)(long)index);
+        } else {
         dev->set_watch(dev, dev->vq[index].kick_fd, VU_WATCH_IN,
                        vu_kick_cb, (void *)(long)index);
-
+        }
         DPRINT("Waiting for kicks on fd: %d for vq: %d\n",
                dev->vq[index].kick_fd, index);
     }
@@ -1097,8 +1111,14 @@ void vu_set_queue_handler(VuDev *dev, VuVirtq *vq,
     vq->handler = handler;
     if (vq->kick_fd >= 0) {
         if (handler) {
+            if (dev->set_watch_packed_data) {
+                dev->set_watch_packed_data(dev, vq->kick_fd, VU_WATCH_IN,
+                                           dev->co_iface->kick_callback,
+                                           (void *)(long)qidx);
+            } else {
             dev->set_watch(dev, vq->kick_fd, VU_WATCH_IN,
                            vu_kick_cb, (void *)(long)qidx);
+            }
         } else {
             dev->remove_watch(dev, vq->kick_fd);
         }
@@ -1627,6 +1647,12 @@ vu_deinit(VuDev *dev)
         }
 
         if (vq->kick_fd != -1) {
+            /* remove watch for kick_fd
+             * When client process is running in gdb and
+             * quit command is run in gdb, QEMU will still dispatch the event
+             * which will cause segment fault in the callback function
+             */
+            dev->remove_watch(dev, vq->kick_fd);
             close(vq->kick_fd);
             vq->kick_fd = -1;
         }
@@ -1682,7 +1708,7 @@ vu_init(VuDev *dev,
 
     assert(max_queues > 0);
     assert(socket >= 0);
-    assert(set_watch);
+    /* assert(set_watch); */
     assert(remove_watch);
     assert(iface);
     assert(panic);
@@ -1715,6 +1741,24 @@ vu_init(VuDev *dev,
     return true;
 }
 
+bool
+vu_init_packed_data(VuDev *dev,
+        uint16_t max_queues,
+        int socket,
+        vu_panic_cb panic,
+        vu_set_watch_cb_packed_data set_watch_packed_data,
+        vu_remove_watch_cb remove_watch,
+        const VuDevIface *iface,
+        const CoIface *co_iface)
+{
+    if (vu_init(dev, max_queues, socket, panic, NULL, remove_watch, iface)) {
+        dev->set_watch_packed_data = set_watch_packed_data;
+        dev->co_iface = co_iface;
+        return true;
+    }
+    return false;
+}
+
 VuVirtq *
 vu_get_queue(VuDev *dev, int qidx)
 {
diff --git a/contrib/libvhost-user/libvhost-user.h 
b/contrib/libvhost-user/libvhost-user.h
index 5cb7708559..6aadeaa0f2 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -30,6 +30,8 @@
 
 #define VHOST_MEMORY_MAX_NREGIONS 8
 
+#define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
+
 typedef enum VhostSetConfigType {
     VHOST_SET_CONFIG_TYPE_MASTER = 0,
     VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
@@ -201,6 +203,7 @@ typedef uint64_t (*vu_get_features_cb) (VuDev *dev);
 typedef void (*vu_set_features_cb) (VuDev *dev, uint64_t features);
 typedef int (*vu_process_msg_cb) (VuDev *dev, VhostUserMsg *vmsg,
                                   int *do_reply);
+typedef bool (*vu_read_msg_cb) (VuDev *dev, int sock, VhostUserMsg *vmsg);
 typedef void (*vu_queue_set_started_cb) (VuDev *dev, int qidx, bool started);
 typedef bool (*vu_queue_is_processed_in_order_cb) (VuDev *dev, int qidx);
 typedef int (*vu_get_config_cb) (VuDev *dev, uint8_t *config, uint32_t len);
@@ -208,6 +211,20 @@ typedef int (*vu_set_config_cb) (VuDev *dev, const uint8_t 
*data,
                                  uint32_t offset, uint32_t size,
                                  uint32_t flags);
 
+typedef void (*vu_watch_cb_packed_data) (void *packed_data);
+
+typedef void (*vu_set_watch_cb_packed_data) (VuDev *dev, int fd, int condition,
+                                             vu_watch_cb_packed_data cb,
+                                             void *data);
+/*
+ * allowing vu_read_msg_cb and kick_callback to be replaced so QEMU
+ * can run them as coroutines
+ */
+typedef struct CoIface {
+    vu_read_msg_cb read_msg;
+    vu_watch_cb_packed_data kick_callback;
+} CoIface;
+
 typedef struct VuDevIface {
     /* called by VHOST_USER_GET_FEATURES to get the features bitmask */
     vu_get_features_cb get_features;
@@ -372,7 +389,8 @@ struct VuDev {
     /* @set_watch: add or update the given fd to the watch set,
      * call cb when condition is met */
     vu_set_watch_cb set_watch;
-
+    /* AIO dispatch will only one data pointer to callback function */
+    vu_set_watch_cb_packed_data set_watch_packed_data;
     /* @remove_watch: remove the given fd from the watch set */
     vu_remove_watch_cb remove_watch;
 
@@ -380,7 +398,7 @@ struct VuDev {
      * re-initialize */
     vu_panic_cb panic;
     const VuDevIface *iface;
-
+    const CoIface *co_iface;
     /* Postcopy data */
     int postcopy_ufd;
     bool postcopy_listening;
@@ -417,6 +435,22 @@ bool vu_init(VuDev *dev,
              const VuDevIface *iface);
 
 
+/**
+ * vu_init_packed_data:
+ * Same as vu_init except for set_watch_packed_data which will pack
+ * two parameters into a struct thus QEMU aio_dispatch can pass the
+ * required data to callback function.
+ *
+ * Returns: true on success, false on failure.
+ **/
+bool vu_init_packed_data(VuDev *dev,
+                         uint16_t max_queues,
+                         int socket,
+                         vu_panic_cb panic,
+                         vu_set_watch_cb_packed_data set_watch_packed_data,
+                         vu_remove_watch_cb remove_watch,
+                         const VuDevIface *iface,
+                         const CoIface *co_iface);
 /**
  * vu_deinit:
  * @dev: a VuDev context
-- 
2.25.0