From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
The loading of a device state (during postcopy) may access guest
memory that's still on the source machine and thus might need
a page fill; split off a separate thread that handles the incoming
page data so that the original incoming migration code can finish
off the device data.
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
---
include/migration/migration.h | 4 +++
migration.c | 6 +++++
savevm.c | 62 +++++++++++++++++++++++++++++++++++++++++--
3 files changed, 70 insertions(+), 2 deletions(-)
diff --git a/include/migration/migration.h b/include/migration/migration.h
index 00255b8..69e776c 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -92,6 +92,10 @@ struct MigrationIncomingState {
QemuThread fault_thread;
QemuSemaphore fault_thread_sem;
+ bool have_listen_thread;
+ QemuThread listen_thread;
+ QemuSemaphore listen_thread_sem;
+
/* For the kernel to send us notifications */
int userfault_fd;
/* To tell the fault_thread to quit */
diff --git a/migration.c b/migration.c
index 63d7699..f0f2e2f 100644
--- a/migration.c
+++ b/migration.c
@@ -1071,6 +1071,12 @@ static int postcopy_start(MigrationState *ms)
return -1;
}
+ /*
+ * Make sure the receiver can get incoming pages before we send the rest
+ * of the state
+ */
+ qemu_savevm_send_postcopy_ram_listen(fb);
+
qemu_savevm_state_complete(fb);
DPRINTF("postcopy_start: sending req 3\n");
qemu_savevm_send_reqack(fb, 3);
diff --git a/savevm.c b/savevm.c
index 859c96f..53e8a2c 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1292,9 +1292,45 @@ static int
loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis,
return 0;
}
+typedef struct ram_listen_thread_data {
+ QEMUFile *f;
+ LoadStateEntry_Head *lh;
+} ram_listen_thread_data;
+
+/*
+ * Triggered by a postcopy_listen command; this thread takes over reading
+ * the input stream, leaving the main thread free to carry on loading the rest
+ * of the device state (from RAM).
+ * (TODO:This could do with being in a postcopy file - but there again it's
+ * just another input loop, not that postcopy specific)
+ */
+static void *postcopy_ram_listen_thread(void *opaque)
+{
+ ram_listen_thread_data *rltd = opaque;
+ MigrationIncomingState *mis = migration_incoming_get_current();
+ int load_res;
+
+ qemu_sem_post(&mis->listen_thread_sem);
+ DPRINTF("postcopy_ram_listen_thread start");
+
+ load_res = qemu_loadvm_state_main(rltd->f, rltd->lh);
+
+ DPRINTF("postcopy_ram_listen_thread exiting");
+ if (load_res < 0) {
+ error_report("%s: loadvm failed: %d", __func__, load_res);
+ qemu_file_set_error(rltd->f, load_res);
+ }
+ postcopy_ram_incoming_cleanup(mis);
+ g_free(rltd);
+
+ return NULL;
+}
+
/* After this message we must be able to immediately receive page data */
static int loadvm_postcopy_ram_handle_listen(MigrationIncomingState *mis)
{
+ ram_listen_thread_data *rltd = g_malloc(sizeof(ram_listen_thread_data));
+
DPRINTF("%s", __func__);
if (mis->postcopy_ram_state != POSTCOPY_RAM_INCOMING_ADVISE) {
error_report("CMD_POSTCOPY_RAM_LISTEN in wrong postcopy state (%d)",
@@ -1313,8 +1349,25 @@ static int
loadvm_postcopy_ram_handle_listen(MigrationIncomingState *mis)
return -1;
}
- /* TODO start up the postcopy listening thread */
- return 0;
+ if (mis->have_listen_thread) {
+ error_report("CMD_POSTCOPY_RAM_LISTEN already has a listen thread");
+ return -1;
+ }
+
+ mis->have_listen_thread = true;
+ /* Start up the listening thread and wait for it to signal ready */
+ qemu_sem_init(&mis->listen_thread_sem, 0);
+ rltd->f = mis->file;
+ rltd->lh = &loadvm_handlers;
+ qemu_thread_create(&mis->listen_thread, "postcopy/listen",
+ postcopy_ram_listen_thread, rltd, QEMU_THREAD_JOINABLE);
+ qemu_sem_wait(&mis->listen_thread_sem);
+
+ /*
+ * all good - cause the loop that handled this command to exit because
+ * the new thread is taking over
+ */
+ return LOADVM_EXITCODE_QUITPARENT | LOADVM_EXITCODE_KEEPHANDLERS;
}
/* After all discards we can start running and asking for pages */
@@ -1640,6 +1693,11 @@ int qemu_loadvm_state(QEMUFile *f)
QLIST_INIT(&loadvm_handlers);
ret = qemu_loadvm_state_main(f, &loadvm_handlers);
+ if (migration_incoming_get_current()->have_listen_thread) {
+ /* Listen thread still going, can't clean up yet */
+ return ret;
+ }
+
if (ret == 0) {
cpu_synchronize_all_post_init();
}
--
1.9.3
