[Qemu-devel] [PATCH v6 09/13] vfio: Add save state functions to SaveVMHandlers

[Kirti Wankhede]

Added .save_live_pending, .save_live_iterate and .save_live_complete_precopy
functions. These functions handles pre-copy and stop-and-copy phase.

In _SAVING|_RUNNING device state or pre-copy phase:
- read pending_bytes
- read data_offset - indicates kernel driver to write data to staging
  buffer which is mmapped.
- read data_size - amount of data in bytes written by vendor driver in migration
  region.
- if data section is trapped, pread() from data_offset of data_size.
- if data section is mmaped, read mmaped buffer of data_size.
- Write data packet to file stream as below:
{VFIO_MIG_FLAG_DEV_DATA_STATE, data_size, actual data,
VFIO_MIG_FLAG_END_OF_STATE }

In _SAVING device state or stop-and-copy phase
a. read config space of device and save to migration file stream. This
   doesn't need to be from vendor driver. Any other special config state
   from driver can be saved as data in following iteration.
b. read pending_bytes
c. read data_offset - indicates kernel driver to write data to staging
   buffer which is mmapped.
d. read data_size - amount of data in bytes written by vendor driver in
   migration region.
e. if data section is trapped, pread() from data_offset of data_size.
f. if data section is mmaped, read mmaped buffer of data_size.
g. Write data packet as below:
   {VFIO_MIG_FLAG_DEV_DATA_STATE, data_size, actual data}
h. iterate through steps b to g while (pending_bytes > 0)
i. Write {VFIO_MIG_FLAG_END_OF_STATE}

When data region is mapped, its user's responsibility to read data from
data_offset of data_size before moving to next steps.

.save_live_iterate runs outside the iothread lock in the migration case, which
could race with asynchronous call to get dirty page list causing data corruption
in mapped migration region. Mutex added here to serial migration buffer read
operation.

Signed-off-by: Kirti Wankhede <address@hidden>
Reviewed-by: Neo Jia <address@hidden>
---
 hw/vfio/migration.c  | 246 +++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/vfio/trace-events |   6 ++
 2 files changed, 252 insertions(+)

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 0597a45fda2d..4e9b4cce230b 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -117,6 +117,138 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, 
uint32_t state)
     return 0;
 }
 
+static void *find_data_region(VFIORegion *region,
+                              uint64_t data_offset,
+                              uint64_t data_size)
+{
+    void *ptr = NULL;
+    int i;
+
+    for (i = 0; i < region->nr_mmaps; i++) {
+        if ((data_offset >= region->mmaps[i].offset) &&
+            (data_offset < region->mmaps[i].offset + region->mmaps[i].size) &&
+            (data_size <= region->mmaps[i].size)) {
+            ptr = region->mmaps[i].mmap + (data_offset -
+                                           region->mmaps[i].offset);
+            break;
+        }
+    }
+    return ptr;
+}
+
+static int vfio_save_buffer(QEMUFile *f, VFIODevice *vbasedev)
+{
+    VFIOMigration *migration = vbasedev->migration;
+    VFIORegion *region = &migration->region.buffer;
+    uint64_t data_offset = 0, data_size = 0;
+    int ret;
+
+    ret = pread(vbasedev->fd, &data_offset, sizeof(data_offset),
+                region->fd_offset + offsetof(struct vfio_device_migration_info,
+                                             data_offset));
+    if (ret != sizeof(data_offset)) {
+        error_report("%s: Failed to get migration buffer data offset %d",
+                     vbasedev->name, ret);
+        return -EINVAL;
+    }
+
+    ret = pread(vbasedev->fd, &data_size, sizeof(data_size),
+                region->fd_offset + offsetof(struct vfio_device_migration_info,
+                                             data_size));
+    if (ret != sizeof(data_size)) {
+        error_report("%s: Failed to get migration buffer data size %d",
+                     vbasedev->name, ret);
+        return -EINVAL;
+    }
+
+    if (data_size > 0) {
+        void *buf = NULL;
+        bool buffer_mmaped;
+
+        if (region->mmaps) {
+            buf = find_data_region(region, data_offset, data_size);
+        }
+
+        buffer_mmaped = (buf != NULL) ? true : false;
+
+        if (!buffer_mmaped) {
+            buf = g_try_malloc0(data_size);
+            if (!buf) {
+                error_report("%s: Error allocating buffer ", __func__);
+                return -ENOMEM;
+            }
+
+            ret = pread(vbasedev->fd, buf, data_size,
+                        region->fd_offset + data_offset);
+            if (ret != data_size) {
+                error_report("%s: Failed to get migration data %d",
+                             vbasedev->name, ret);
+                g_free(buf);
+                return -EINVAL;
+            }
+        }
+
+        qemu_put_be64(f, data_size);
+        qemu_put_buffer(f, buf, data_size);
+
+        if (!buffer_mmaped) {
+            g_free(buf);
+        }
+        migration->pending_bytes -= data_size;
+    } else {
+        qemu_put_be64(f, data_size);
+    }
+
+    trace_vfio_save_buffer(vbasedev->name, data_offset, data_size,
+                           migration->pending_bytes);
+
+    ret = qemu_file_get_error(f);
+    if (ret) {
+        return ret;
+    }
+
+    return data_size;
+}
+
+static int vfio_update_pending(VFIODevice *vbasedev)
+{
+    VFIOMigration *migration = vbasedev->migration;
+    VFIORegion *region = &migration->region.buffer;
+    uint64_t pending_bytes = 0;
+    int ret;
+
+    ret = pread(vbasedev->fd, &pending_bytes, sizeof(pending_bytes),
+                region->fd_offset + offsetof(struct vfio_device_migration_info,
+                                             pending_bytes));
+    if ((ret < 0) || (ret != sizeof(pending_bytes))) {
+        error_report("%s: Failed to get pending bytes %d",
+                     vbasedev->name, ret);
+        migration->pending_bytes = 0;
+        return (ret < 0) ? ret : -EINVAL;
+    }
+
+    migration->pending_bytes = pending_bytes;
+    trace_vfio_update_pending(vbasedev->name, pending_bytes);
+    return 0;
+}
+
+static int vfio_save_device_config_state(QEMUFile *f, void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+
+    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_CONFIG_STATE);
+
+    if (vbasedev->ops && vbasedev->ops->vfio_save_config) {
+        vbasedev->ops->vfio_save_config(vbasedev, f);
+    }
+
+    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+
+    trace_vfio_save_device_config_state(vbasedev->name);
+
+    return qemu_file_get_error(f);
+}
+
 /* ---------------------------------------------------------------------- */
 
 static int vfio_save_setup(QEMUFile *f, void *opaque)
@@ -178,9 +310,123 @@ static void vfio_save_cleanup(void *opaque)
     trace_vfio_save_cleanup(vbasedev->name);
 }
 
+static void vfio_save_pending(QEMUFile *f, void *opaque,
+                              uint64_t threshold_size,
+                              uint64_t *res_precopy_only,
+                              uint64_t *res_compatible,
+                              uint64_t *res_postcopy_only)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+    int ret;
+
+    ret = vfio_update_pending(vbasedev);
+    if (ret) {
+        return;
+    }
+
+    *res_precopy_only += migration->pending_bytes;
+
+    trace_vfio_save_pending(vbasedev->name, *res_precopy_only,
+                            *res_postcopy_only, *res_compatible);
+}
+
+static int vfio_save_iterate(QEMUFile *f, void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+    int ret, data_size;
+
+    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
+
+    qemu_mutex_lock(&migration->lock);
+    data_size = vfio_save_buffer(f, vbasedev);
+    qemu_mutex_unlock(&migration->lock);
+
+    if (data_size < 0) {
+        error_report("%s: vfio_save_buffer failed %s", vbasedev->name,
+                     strerror(errno));
+        return data_size;
+    }
+
+    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+
+    ret = qemu_file_get_error(f);
+    if (ret) {
+        return ret;
+    }
+
+    trace_vfio_save_iterate(vbasedev->name, data_size);
+    if (data_size == 0) {
+        /* indicates data finished, goto complete phase */
+        return 1;
+    }
+
+    return 0;
+}
+
+static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+    VFIOMigration *migration = vbasedev->migration;
+    int ret;
+
+    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_SAVING);
+    if (ret) {
+        error_report("%s: Failed to set state STOP and SAVING",
+                     vbasedev->name);
+        return ret;
+    }
+
+    ret = vfio_save_device_config_state(f, opaque);
+    if (ret) {
+        return ret;
+    }
+
+    ret = vfio_update_pending(vbasedev);
+    if (ret) {
+        return ret;
+    }
+
+    while (migration->pending_bytes > 0) {
+        qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
+        ret = vfio_save_buffer(f, vbasedev);
+        if (ret < 0) {
+            error_report("%s: Failed to save buffer", vbasedev->name);
+            return ret;
+        } else if (ret == 0) {
+            break;
+        }
+
+        ret = vfio_update_pending(vbasedev);
+        if (ret) {
+            return ret;
+        }
+    }
+
+    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
+
+    ret = qemu_file_get_error(f);
+    if (ret) {
+        return ret;
+    }
+
+    ret = vfio_migration_set_state(vbasedev, ~VFIO_DEVICE_STATE_MASK);
+    if (ret) {
+        error_report("%s: Failed to set state STOPPED", vbasedev->name);
+        return ret;
+    }
+
+    trace_vfio_save_complete_precopy(vbasedev->name);
+    return ret;
+}
+
 static SaveVMHandlers savevm_vfio_handlers = {
     .save_setup = vfio_save_setup,
     .save_cleanup = vfio_save_cleanup,
+    .save_live_pending = vfio_save_pending,
+    .save_live_iterate = vfio_save_iterate,
+    .save_live_complete_precopy = vfio_save_complete_precopy,
 };
 
 /* ---------------------------------------------------------------------- */
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index 4bb43f18f315..e21da4773af3 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -151,3 +151,9 @@ vfio_vmstate_change(char *name, int running, const char 
*reason, uint32_t dev_st
 vfio_migration_state_notifier(char *name, int state) " (%s) state %d"
 vfio_save_setup(char *name) " (%s)"
 vfio_save_cleanup(char *name) " (%s)"
+vfio_save_buffer(char *name, uint64_t data_offset, uint64_t data_size, 
uint64_t pending) " (%s), Offset 0x%"PRIx64" size 0x%"PRIx64" pending 0x%"PRIx64
+vfio_update_pending(char *name, uint64_t pending) " (%s), pending 0x%"PRIx64
+vfio_save_device_config_state(char *name) " (%s)"
+vfio_save_pending(char *name, uint64_t precopy, uint64_t postcopy, uint64_t 
compatible) " (%s), precopy 0x%"PRIx64" postcopy 0x%x"PRIx64" compatible 
0x%"PRIx64
+vfio_save_iterate(char *name, int data_size) " (%s) data_size %d"
+vfio_save_complete_precopy(char *name) " (%s)"
-- 
2.7.0