[PATCH RFC 26/26] vfio/migration: Multifd device state transfer support - send side

[Maciej S. Szmigiero]

From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

Implement the multifd device state transfer via additional per-device
thread spawned from save_live_complete_precopy_async handler.

Switch between doing the data transfer in the new handler and doing it
in the old save_state handler depending on the
migration_has_device_state_support() return value.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 hw/vfio/migration.c           | 195 ++++++++++++++++++++++++++++++++++
 hw/vfio/trace-events          |   3 +
 include/hw/vfio/vfio-common.h |   8 ++
 3 files changed, 206 insertions(+)

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 3af62dea6899..6177431a0cd3 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -608,11 +608,15 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
     return qemu_file_get_error(f);
 }
 
+static void 
vfio_save_complete_precopy_async_thread_thread_terminate(VFIODevice *vbasedev);
+
 static void vfio_save_cleanup(void *opaque)
 {
     VFIODevice *vbasedev = opaque;
     VFIOMigration *migration = vbasedev->migration;
 
+    vfio_save_complete_precopy_async_thread_thread_terminate(vbasedev);
+
     /*
      * Changing device state from STOP_COPY to STOP can take time. Do it here,
      * after migration has completed, so it won't increase downtime.
@@ -621,6 +625,7 @@ static void vfio_save_cleanup(void *opaque)
         vfio_migration_set_state_or_reset(vbasedev, VFIO_DEVICE_STATE_STOP);
     }
 
+    g_clear_pointer(&migration->idstr, g_free);
     g_free(migration->data_buffer);
     migration->data_buffer = NULL;
     migration->precopy_init_size = 0;
@@ -735,6 +740,12 @@ static int vfio_save_complete_precopy(QEMUFile *f, void 
*opaque)
     ssize_t data_size;
     int ret;
 
+    if (migration_has_device_state_support()) {
+        /* Emit dummy NOP data */
+        qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+        return 0;
+    }
+
     trace_vfio_save_complete_precopy_started(vbasedev->name);
 
     /* We reach here with device state STOP or STOP_COPY only */
@@ -762,11 +773,186 @@ static int vfio_save_complete_precopy(QEMUFile *f, void 
*opaque)
     return ret;
 }
 
+static int vfio_save_complete_precopy_async_thread_config_state(VFIODevice 
*vbasedev, uint32_t idx)
+{
+    VFIOMigration *migration = vbasedev->migration;
+    g_autoptr(QIOChannelBuffer) bioc = NULL;
+    QEMUFile *f = NULL;
+    int ret;
+    g_autofree VFIODeviceStatePacket *packet = NULL;
+    size_t packet_len;
+
+    bioc = qio_channel_buffer_new(0);
+    qio_channel_set_name(QIO_CHANNEL(bioc), "vfio-device-config-save");
+
+    f = qemu_file_new_output(QIO_CHANNEL(bioc));
+
+    ret = vfio_save_device_config_state(f, vbasedev);
+    if (ret) {
+        return ret;
+    }
+
+    ret = qemu_fflush(f);
+    if (ret) {
+        goto ret_close_file;
+    }
+
+    packet_len = sizeof(*packet) + bioc->usage;
+    packet = g_malloc0(packet_len);
+    packet->idx = idx;
+    packet->flags = VFIO_DEVICE_STATE_CONFIG_STATE;
+    memcpy(&packet->data, bioc->data, bioc->usage);
+
+    ret = multifd_queue_device_state(migration->idstr, migration->instance_id,
+                                     (char *)packet, packet_len);
+
+    bytes_transferred += packet_len;
+
+ret_close_file:
+    g_clear_pointer(&f, qemu_fclose);
+    return ret;
+}
+
+static void *vfio_save_complete_precopy_async_thread(void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+    int *ret = &migration->save_complete_precopy_thread_ret;
+    g_autofree VFIODeviceStatePacket *packet = NULL;
+    uint32_t idx;
+
+    /* We reach here with device state STOP or STOP_COPY only */
+    *ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
+                                    VFIO_DEVICE_STATE_STOP);
+    if (*ret) {
+        return NULL;
+    }
+
+    packet = g_malloc0(sizeof(*packet) + migration->data_buffer_size);
+
+    for (idx = 0; ; idx++) {
+        ssize_t data_size;
+        size_t packet_size;
+
+        data_size = read(migration->data_fd, &packet->data,
+                         migration->data_buffer_size);
+        if (data_size < 0) {
+            if (errno != ENOMSG) {
+                *ret = -errno;
+                return NULL;
+            }
+
+            /*
+             * Pre-copy emptied all the device state for now. For more 
information,
+             * please refer to the Linux kernel VFIO uAPI.
+             */
+            data_size = 0;
+        }
+
+        if (data_size == 0)
+            break;
+
+        packet->idx = idx;
+        packet_size = sizeof(*packet) + data_size;
+
+        *ret = multifd_queue_device_state(migration->idstr, 
migration->instance_id,
+                                          (char *)packet, packet_size);
+        if (*ret) {
+            return NULL;
+        }
+
+        bytes_transferred += packet_size;
+    }
+
+    *ret = vfio_save_complete_precopy_async_thread_config_state(vbasedev, idx);
+    if (*ret) {
+        return NULL;
+    }
+
+    trace_vfio_save_complete_precopy_async_finished(vbasedev->name);
+
+    return NULL;
+}
+
+static int vfio_save_complete_precopy_async(QEMUFile *f,
+                                            char *idstr, uint32_t instance_id,
+                                            void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+    int ret;
+
+    migration->save_complete_precopy_thread_ret = 0;
+
+    if (!migration_has_device_state_support()) {
+        /* Emit dummy NOP data */
+        qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+        return 0;
+    }
+
+    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE_COMPLETE);
+    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+
+    ret = qemu_fflush(f);
+    if (ret) {
+        return ret;
+    }
+
+    assert(!migration->save_complete_precopy_thread_started);
+
+    assert(!migration->idstr);
+    migration->idstr = g_strdup(idstr);
+    migration->instance_id = instance_id;
+
+    qemu_thread_create(&migration->save_complete_precopy_thread,
+                       "vfio-save_complete_precopy",
+                       vfio_save_complete_precopy_async_thread,
+                       opaque, QEMU_THREAD_JOINABLE);
+
+    migration->save_complete_precopy_thread_started = true;
+
+    trace_vfio_save_complete_precopy_async_started(vbasedev->name, idstr, 
instance_id);
+
+    return 0;
+}
+
+static void 
vfio_save_complete_precopy_async_thread_thread_terminate(VFIODevice *vbasedev)
+{
+    VFIOMigration *migration = vbasedev->migration;
+
+    if (!migration->save_complete_precopy_thread_started) {
+        return;
+    }
+
+    qemu_thread_join(&migration->save_complete_precopy_thread);
+
+    migration->save_complete_precopy_thread_started = false;
+
+    trace_vfio_save_complete_precopy_async_joined(vbasedev->name,
+                                                  
migration->save_complete_precopy_thread_ret);
+}
+
+static int vfio_save_complete_precopy_async_wait(QEMUFile *f, void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+
+    vfio_save_complete_precopy_async_thread_thread_terminate(vbasedev);
+
+    return migration->save_complete_precopy_thread_ret;
+}
+
 static void vfio_save_state(QEMUFile *f, void *opaque)
 {
     VFIODevice *vbasedev = opaque;
     int ret;
 
+    if (migration_has_device_state_support()) {
+        /* Emit dummy NOP data */
+        qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+        return;
+    }
+
     ret = vfio_save_device_config_state(f, opaque);
     if (ret) {
         error_report("%s: Failed to save device config space",
@@ -1014,6 +1200,8 @@ static const SaveVMHandlers savevm_vfio_handlers = {
     .state_pending_exact = vfio_state_pending_exact,
     .is_active_iterate = vfio_is_active_iterate,
     .save_live_iterate = vfio_save_iterate,
+    .save_live_complete_precopy_async = vfio_save_complete_precopy_async,
+    .save_live_complete_precopy_async_wait = 
vfio_save_complete_precopy_async_wait,
     .save_live_complete_precopy = vfio_save_complete_precopy,
     .save_state = vfio_save_state,
     .load_setup = vfio_load_setup,
@@ -1034,6 +1222,10 @@ static void vfio_vmstate_change_prepare(void *opaque, 
bool running,
     enum vfio_device_mig_state new_state;
     int ret;
 
+    if (running) {
+        vfio_save_complete_precopy_async_thread_thread_terminate(vbasedev);
+    }
+
     new_state = migration->device_state == VFIO_DEVICE_STATE_PRE_COPY ?
                     VFIO_DEVICE_STATE_PRE_COPY_P2P :
                     VFIO_DEVICE_STATE_RUNNING_P2P;
@@ -1059,6 +1251,9 @@ static void vfio_vmstate_change(void *opaque, bool 
running, RunState state)
     int ret;
 
     if (running) {
+        /* In case "prepare" callback wasn't registered */
+        vfio_save_complete_precopy_async_thread_thread_terminate(vbasedev);
+
         new_state = VFIO_DEVICE_STATE_RUNNING;
     } else {
         new_state =
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index 569bb6897b66..44c7bb01a004 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -165,6 +165,9 @@ vfio_save_block(const char *name, int data_size) " (%s) 
data_size %d"
 vfio_save_cleanup(const char *name) " (%s)"
 vfio_save_complete_precopy(const char *name, int ret) " (%s) ret %d"
 vfio_save_complete_precopy_started(const char *name) " (%s)"
+vfio_save_complete_precopy_async_started(const char *name, const char *idstr, 
uint32_t instance_id) " (%s) idstr %s instance %"PRIu32
+vfio_save_complete_precopy_async_finished(const char *name) " (%s)"
+vfio_save_complete_precopy_async_joined(const char *name, int ret) " (%s) ret 
%d"
 vfio_save_device_config_state(const char *name) " (%s)"
 vfio_save_iterate(const char *name, uint64_t precopy_init_size, uint64_t 
precopy_dirty_size) " (%s) precopy initial size 0x%"PRIx64" precopy dirty size 
0x%"PRIx64
 vfio_save_iterate_started(const char *name) " (%s)"
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index f861cbd13384..0c51b8bf4d9a 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -74,12 +74,20 @@ typedef struct VFIOMigration {
 
     bool save_iterate_run;
     bool save_iterate_empty_hit;
+
+    QemuThread save_complete_precopy_thread;
+    int save_complete_precopy_thread_ret;
+    bool save_complete_precopy_thread_started;
+
     QemuThread load_bufs_thread;
     Error *load_bufs_thread_errp;
     bool load_bufs_thread_started;
     bool load_bufs_thread_finished;
     bool load_bufs_thread_want_exit;
 
+    char *idstr;
+    uint32_t instance_id;
+
     GArray *load_bufs;
     bool load_bufs_device_ready;
     GCond load_bufs_device_ready_cond;