On 27/08/2024 20:54, Maciej S. Szmigiero wrote:
External email: Use caution opening links or attachments
From: "Maciej S. Szmigiero" <maciej.szmigi...@oracle.com>
Implement the multifd device state transfer via additional per-device
thread inside save_live_complete_precopy_thread handler.
Switch between doing the data transfer in the new handler and doing it
in the old save_state handler depending on the
x-migration-multifd-transfer device property value.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigi...@oracle.com>
---
hw/vfio/migration.c | 169 ++++++++++++++++++++++++++++++++++
hw/vfio/trace-events | 2 +
include/hw/vfio/vfio-common.h | 1 +
3 files changed, 172 insertions(+)
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 57c1542528dc..67996aa2df8b 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -655,6 +655,16 @@ static int vfio_save_setup(QEMUFile *f, void *opaque,
Error **errp)
uint64_t stop_copy_size = VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE;
int ret;
+ /* Make a copy of this setting at the start in case it is changed
mid-migration */
+ migration->multifd_transfer = vbasedev->migration_multifd_transfer;
Should VFIO multifd be controlled by main migration multifd capability,
and let the per VFIO device migration_multifd_transfer property be
immutable and enabled by default?
Then we would have a single point of configuration (and an extra one per
VFIO device just to disable for backward compatibility).
Unless there are other benefits to have this property configurable?
+
+ if (migration->multifd_transfer && !migration_has_device_state_support()) {
+ error_setg(errp,
+ "%s: Multifd device transfer requested but unsupported in the
current config",
+ vbasedev->name);
+ return -EINVAL;
+ }
+
qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE);
vfio_query_stop_copy_size(vbasedev, &stop_copy_size);
@@ -835,10 +845,20 @@ static int vfio_save_iterate(QEMUFile *f, void *opaque)
static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
{
VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
ssize_t data_size;
int ret;
Error *local_err = NULL;
+ if (migration->multifd_transfer) {
+ /*
+ * Emit dummy NOP data, vfio_save_complete_precopy_thread()
+ * does the actual transfer.
+ */
+ qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
There are three places where we send this dummy end of state, maybe
worth extracting it to a helper? I.e., vfio_send_end_of_state() and then
document there the rationale.
+ return 0;
+ }
+
trace_vfio_save_complete_precopy_started(vbasedev->name);
/* We reach here with device state STOP or STOP_COPY only */
@@ -864,12 +884,159 @@ static int vfio_save_complete_precopy(QEMUFile *f, void
*opaque)
return ret;
}
+static int vfio_save_complete_precopy_async_thread_config_state(VFIODevice
*vbasedev,
+ char *idstr,
+ uint32_t
instance_id,
+ uint32_t idx)
+{
+ 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, NULL);
+ if (ret) {
+ return ret;
Need to close f in this case.
+ }
+
+ 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);
+
+ if (!multifd_queue_device_state(idstr, instance_id,
+ (char *)packet, packet_len)) {
+ ret = -1;
goto ret_close_file?
+ }
+
+ bytes_transferred += packet_len;
bytes_transferred is a global variable. Now that we access it from
multiple threads it should be protected.
Note that now the VFIO device data is reported also in multifd stats (if
I am not mistaken), is this the behavior we want? Maybe we should
enhance multifd stats to distinguish between RAM data and device data?
+
+ret_close_file:
Rename to "out" as we only have one exit point?
+ g_clear_pointer(&f, qemu_fclose);
f is a local variable, wouldn't qemu_fclose(f) be enough here?
+ return ret;
+}
+
+static int vfio_save_complete_precopy_thread(char *idstr,
+ uint32_t instance_id,
+ bool *abort_flag,
+ void *opaque)
+{
+ VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
+ int ret;
+ g_autofree VFIODeviceStatePacket *packet = NULL;
+ uint32_t idx;
+
+ if (!migration->multifd_transfer) {
+ /* Nothing to do, vfio_save_complete_precopy() does the transfer. */
+ return 0;
+ }
+
+ trace_vfio_save_complete_precopy_thread_started(vbasedev->name,
+ idstr, instance_id);
+
+ /* 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, NULL);
+ if (ret) {
+ goto ret_finish;
+ }
+
+ packet = g_malloc0(sizeof(*packet) + migration->data_buffer_size);
+
+ for (idx = 0; ; idx++) {
+ ssize_t data_size;
+ size_t packet_size;
+
+ if (qatomic_read(abort_flag)) {
+ ret = -ECANCELED;
+ goto ret_finish;
+ }
+
+ data_size = read(migration->data_fd, &packet->data,
+ migration->data_buffer_size);
+ if (data_size < 0) {
+ if (errno != ENOMSG) {
+ ret = -errno;
+ goto ret_finish;
+ }
+
+ /*
+ * Pre-copy emptied all the device state for now. For more
information,
+ * please refer to the Linux kernel VFIO uAPI.
+ */
+ data_size = 0;
According to VFIO uAPI, ENOMSG can only be returned in the PRE_COPY
device states.
Here we are in STOP_COPY, so we can drop the ENOMSG handling.
Thanks.
+ }
+
+ if (data_size == 0)
+ break;
+
+ packet->idx = idx;
+ packet_size = sizeof(*packet) + data_size;
+
+ if (!multifd_queue_device_state(idstr, instance_id,
+ (char *)packet, packet_size)) {
+ ret = -1;
+ goto ret_finish;
+ }
+
+ bytes_transferred += packet_size;
+ }
+
+ ret = vfio_save_complete_precopy_async_thread_config_state(vbasedev, idstr,
+ instance_id,
+ idx);
+
+ret_finish:
+ trace_vfio_save_complete_precopy_thread_finished(vbasedev->name, ret);
+
+ return ret;
+}
+
+static int vfio_save_complete_precopy_begin(QEMUFile *f,
+ char *idstr, uint32_t instance_id,
+ void *opaque)
+{
+ VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
+
+ if (!migration->multifd_transfer) {
+ /* 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);
+
+ return qemu_fflush(f);
+}
+
static void vfio_save_state(QEMUFile *f, void *opaque)
{
VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
Error *local_err = NULL;
int ret;
+ if (migration->multifd_transfer) {
+ /* Emit dummy NOP data */
+ qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+ return;
+ }
+
ret = vfio_save_device_config_state(f, opaque, &local_err);
if (ret) {
error_prepend(&local_err,
@@ -1119,7 +1286,9 @@ 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_begin = vfio_save_complete_precopy_begin,
.save_live_complete_precopy = vfio_save_complete_precopy,
+ .save_live_complete_precopy_thread = vfio_save_complete_precopy_thread,
.save_state = vfio_save_state,
.load_setup = vfio_load_setup,
.load_cleanup = vfio_load_cleanup,
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index 9d2519a28a7e..b1d9c9d5f2e1 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -167,6 +167,8 @@ 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_thread_started(const char *name, const char *idstr, uint32_t
instance_id) " (%s) idstr %s instance %"PRIu32
+vfio_save_complete_precopy_thread_finished(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 fe05acb9a5d1..4578a0ca6a5c 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -72,6 +72,7 @@ typedef struct VFIOMigration {
uint64_t mig_flags;
uint64_t precopy_init_size;
uint64_t precopy_dirty_size;
+ bool multifd_transfer;
bool initial_data_sent;
bool save_iterate_run;
