Currently, if IOMMU of a VFIO container doesn't support dirty page
tracking, migration is blocked completely. This is because a DMA-able
VFIO device can dirty RAM pages without updating QEMU about it, thus
breaking the migration.
However, this doesn't mean that migration can't be done at all. If
migration pre-copy phase is skipped, the VFIO device doesn't have a
chance to dirty RAM pages that have been migrated already, thus
eliminating the problem previously mentioned.
Hence, in such case allow migration but skip pre-copy phase.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
---
hw/vfio/migration.c | 9 ++++++++-
migration/migration.c | 5 +++++
migration/migration.h | 3 +++
3 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 34f9f894ed..d8f9b086c2 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -863,10 +863,17 @@ int vfio_migration_probe(VFIODevice *vbasedev,
Error **errp)
struct vfio_region_info *info = NULL;
int ret = -ENOTSUP;
- if (!vbasedev->enable_migration ||
!container->dirty_pages_supported) {
+ if (!vbasedev->enable_migration) {
goto add_blocker;
}
+ if (!container->dirty_pages_supported) {
+ warn_report_once(
+ "%s: IOMMU of the device's VFIO container doesn't
support dirty page tracking, migration pre-copy phase will be skipped",
+ vbasedev->name);
+ migrate_get_current()->skip_precopy = true;
+ }
+
ret = vfio_get_dev_region_info(vbasedev,
VFIO_REGION_TYPE_MIGRATION_DEPRECATED,
VFIO_REGION_SUBTYPE_MIGRATION_DEPRECATED,
diff --git a/migration/migration.c b/migration/migration.c
index 31739b2af9..217f0e3e94 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3636,6 +3636,11 @@ static MigIterateState
migration_iteration_run(MigrationState *s)
uint64_t pending_size, pend_pre, pend_compat, pend_post;
bool in_postcopy = s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE;
+ if (s->skip_precopy) {
+ migration_completion(s);
+ return MIG_ITERATE_BREAK;
+ }
+
qemu_savevm_state_pending(s->to_dst_file, s->threshold_size,
&pend_pre,
&pend_compat, &pend_post);
pending_size = pend_pre + pend_compat + pend_post;
diff --git a/migration/migration.h b/migration/migration.h
index 485d58b95f..0920a0950e 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -332,6 +332,9 @@ struct MigrationState {
* This save hostname when out-going migration starts
*/
char *hostname;
+
+ /* Whether to skip pre-copy phase of migration or not */
+ bool skip_precopy;
};
void migrate_set_state(int *state, int old_state, int new_state);