On 1/30/25 11:08, Maciej S. Szmigiero wrote:
From: "Maciej S. Szmigiero" <maciej.szmigi...@oracle.com>
The multifd received data needs to be reassembled since device state
packets sent via different multifd channels can arrive out-of-order.
Therefore, each VFIO device state packet carries a header indicating its
position in the stream.
The raw device state data is saved into a VFIOStateBuffer for later
in-order loading into the device.
The last such VFIO device state packet should have
VFIO_DEVICE_STATE_CONFIG_STATE flag set and carry the device config state.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigi...@oracle.com>
---
hw/vfio/migration.c | 116 ++++++++++++++++++++++++++++++++++
hw/vfio/pci.c | 2 +
hw/vfio/trace-events | 1 +
include/hw/vfio/vfio-common.h | 1 +
4 files changed, 120 insertions(+)
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index bcdf204d5cf4..0c0caec1bd64 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -301,6 +301,12 @@ typedef struct VFIOStateBuffer {
} VFIOStateBuffer;
typedef struct VFIOMultifd {
+ VFIOStateBuffers load_bufs;
+ QemuCond load_bufs_buffer_ready_cond;
+ QemuMutex load_bufs_mutex; /* Lock order: this lock -> BQL */
+ uint32_t load_buf_idx;
+ uint32_t load_buf_idx_last;
+ uint32_t load_buf_queued_pending_buffers;
} VFIOMultifd;
static void vfio_state_buffer_clear(gpointer data)
@@ -346,6 +352,103 @@ static VFIOStateBuffer
*vfio_state_buffers_at(VFIOStateBuffers *bufs, guint idx)
return &g_array_index(bufs->array, VFIOStateBuffer, idx);
}
Each routine executed from a migration thread should have a preliminary
comment saying from which context it is called: migration or VFIO
+static bool vfio_load_state_buffer_insert(VFIODevice *vbasedev,
+ VFIODeviceStatePacket *packet,
+ size_t packet_total_size,
+ Error **errp)
+{
+ VFIOMigration *migration = vbasedev->migration;
+ VFIOMultifd *multifd = migration->multifd;
+ VFIOStateBuffer *lb;
+
+ vfio_state_buffers_assert_init(&multifd->load_bufs);
+ if (packet->idx >= vfio_state_buffers_size_get(&multifd->load_bufs)) {
+ vfio_state_buffers_size_set(&multifd->load_bufs, packet->idx + 1);
+ }
+
+ lb = vfio_state_buffers_at(&multifd->load_bufs, packet->idx);
+ if (lb->is_present) {
+ error_setg(errp, "state buffer %" PRIu32 " already filled",
+ packet->idx);
+ return false;
+ }
+
+ assert(packet->idx >= multifd->load_buf_idx);
+
+ multifd->load_buf_queued_pending_buffers++;
+ if (multifd->load_buf_queued_pending_buffers >
+ vbasedev->migration_max_queued_buffers) {
+ error_setg(errp,
+ "queuing state buffer %" PRIu32 " would exceed the max of
%" PRIu64,
+ packet->idx, vbasedev->migration_max_queued_buffers);
+ return false;
+ }
AFAICT, attributes multifd->load_buf_queued_pending_buffers and
vbasedev->migration_max_queued_buffers are not strictly necessary.
They allow to count buffers and check an arbitrary limit, which
is UINT64_MAX today. It makes me wonder how useful they are.
Please introduce them in a separate patch at the end of the series,
adding documentation on the "x-migration-max-queued-buffers" property
and also general documentation on why and how to use it.
+
+ lb->data = g_memdup2(&packet->data, packet_total_size - sizeof(*packet));
+ lb->len = packet_total_size - sizeof(*packet);
+ lb->is_present = true;
+
+ return true;
+}
+
+static bool vfio_load_state_buffer(void *opaque, char *data, size_t data_size,
+ Error **errp)
+{
+ VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
+ VFIOMultifd *multifd = migration->multifd;
+ VFIODeviceStatePacket *packet = (VFIODeviceStatePacket *)data;
+
+ /*
+ * Holding BQL here would violate the lock order and can cause
+ * a deadlock once we attempt to lock load_bufs_mutex below.
+ */
+ assert(!bql_locked());
+
+ if (!migration->multifd_transfer) {
+ error_setg(errp,
+ "got device state packet but not doing multifd transfer");
+ return false;
+ }
+
+ assert(multifd);
+
+ if (data_size < sizeof(*packet)) {
+ error_setg(errp, "packet too short at %zu (min is %zu)",
+ data_size, sizeof(*packet));
+ return false;
+ }
+
+ if (packet->version != 0) {
Please add a define for version, even if 0.
+ error_setg(errp, "packet has unknown version %" PRIu32,
+ packet->version);
+ return false;
+ }
+
+ if (packet->idx == UINT32_MAX) {
+ error_setg(errp, "packet has too high idx %" PRIu32,
+ packet->idx);
I don't think printing out packet->idx is useful here.
+ return false;
+ }
+
+ trace_vfio_load_state_device_buffer_incoming(vbasedev->name, packet->idx);
I wonder if we can add thread ids to trace events. It would be useful.
+
+ QEMU_LOCK_GUARD(&multifd->load_bufs_mutex);
+
+ /* config state packet should be the last one in the stream */
+ if (packet->flags & VFIO_DEVICE_STATE_CONFIG_STATE) {
+ multifd->load_buf_idx_last = packet->idx;
+ }
+
+ if (!vfio_load_state_buffer_insert(vbasedev, packet, data_size, errp)) {
So the migration thread calling multifd_device_state_recv() will
exit and the vfio thread loading the state into the device will
hang until its aborted ?
This sequence is expected to be called to release the vfio thread
while (multifd->load_bufs_thread_running) {
multifd->load_bufs_thread_want_exit = true;
qemu_cond_signal(&multifd->load_bufs_buffer_ready_cond);
...
}
right ?
The way the series is presented makes it a bit complex to follow the
proposition, especially regarding the creation and termination of
threads, something the reader should be aware of.
As an initial step in clarifying the design, I would have preferred
a series of patches introducing the various threads, migration threads
and VFIO threads, without any workload. Once the creation and termination
points are established I would then introduce the work load for each
thread.
Thanks,
C.
+ return false;
+ }
+
+ qemu_cond_signal(&multifd->load_bufs_buffer_ready_cond);
+
+ return true;
+}
+
static int vfio_save_device_config_state(QEMUFile *f, void *opaque,
Error **errp)
{
@@ -405,11 +508,23 @@ static VFIOMultifd *vfio_multifd_new(void)
{
VFIOMultifd *multifd = g_new(VFIOMultifd, 1);
+ vfio_state_buffers_init(&multifd->load_bufs);
+
+ qemu_mutex_init(&multifd->load_bufs_mutex);
+
+ multifd->load_buf_idx = 0;
+ multifd->load_buf_idx_last = UINT32_MAX;
+ multifd->load_buf_queued_pending_buffers = 0;
+ qemu_cond_init(&multifd->load_bufs_buffer_ready_cond);
+
return multifd;
}
static void vfio_multifd_free(VFIOMultifd *multifd)
{
+ qemu_cond_destroy(&multifd->load_bufs_buffer_ready_cond);
+ qemu_mutex_destroy(&multifd->load_bufs_mutex);
+
g_free(multifd);
}
@@ -940,6 +1055,7 @@ static const SaveVMHandlers savevm_vfio_handlers = {
.load_setup = vfio_load_setup,
.load_cleanup = vfio_load_cleanup,
.load_state = vfio_load_state,
+ .load_state_buffer = vfio_load_state_buffer,
.switchover_ack_needed = vfio_switchover_ack_needed,
};
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 83090c544d95..2700b355ecf1 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3380,6 +3380,8 @@ static const Property vfio_pci_dev_properties[] = {
DEFINE_PROP_ON_OFF_AUTO("x-migration-load-config-after-iter",
VFIOPCIDevice,
vbasedev.migration_load_config_after_iter,
ON_OFF_AUTO_AUTO),
+ DEFINE_PROP_UINT64("x-migration-max-queued-buffers", VFIOPCIDevice,
+ vbasedev.migration_max_queued_buffers, UINT64_MAX),
DEFINE_PROP_BOOL("migration-events", VFIOPCIDevice,
vbasedev.migration_events, false),
DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false),
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index 1bebe9877d88..042a3dc54a33 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -153,6 +153,7 @@ vfio_load_device_config_state_start(const char *name) "
(%s)"
vfio_load_device_config_state_end(const char *name) " (%s)"
vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64
vfio_load_state_device_data(const char *name, uint64_t data_size, int ret) " (%s) size
%"PRIu64" ret %d"
+vfio_load_state_device_buffer_incoming(const char *name, uint32_t idx) " (%s) idx
%"PRIu32
vfio_migration_realize(const char *name) " (%s)"
vfio_migration_set_device_state(const char *name, const char *state) " (%s) state
%s"
vfio_migration_set_state(const char *name, const char *new_state, const char
*recover_state) " (%s) new state %s, recover state %s"
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index c0c9c0b1b263..0e8b0848882e 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -139,6 +139,7 @@ typedef struct VFIODevice {
OnOffAuto enable_migration;
OnOffAuto migration_multifd_transfer;
OnOffAuto migration_load_config_after_iter;
+ uint64_t migration_max_queued_buffers;
bool migration_events;
VFIODeviceOps *ops;
unsigned int num_irqs;
