Following VFIO migration protocol v2 acceptance in kernel, this series
implements VFIO migration according to the new v2 protocol and replaces
the now deprecated v1 implementation.
The main differences between v1 and v2 migration protocols are:
1. VFIO device state is represented as a finite state machine instead of
2. The migration interface with kernel is done using VFIO_DEVICE_FEATURE
ioctl and normal read() and write() instead of the migration region
used in v1.
3. Pre-copy is made optional in v2 protocol. Support for pre-copy will
be added later on.
Full description of the v2 protocol and the differences from v1 can be
found here .
Patch 1 updates linux headers so we will have the MIG_DATA_SIZE ioctl.
Patches 2-8 are prep patches fixing bugs, adding QEMUFile function
that will be used later and refactoring v1 protocol code to make it
easier to add v2 protocol.
Patches 9-13 implement v2 protocol and remove v1 protocol.
Changes from v7 :
- Fixed compilation error on windows in patch #9 reported by Cedric.
Changes from v6 :
- Fixed another compilation error in patch #9 reported by Cedric.
- Added Reviewed-by tags.
Changes from v5 :
- Dropped patch #3.
- Simplified patch #5 as per Alex's suggestion.
- Changed qemu_file_get_to_fd() to return -EIO instead of -1, as
suggested by Cedric.
Also changed it so now write returns -errno instead of -1 on error.
- Fixed compilation error reported by Cedric.
- Changed vfio_migration_query_flags() to print error message and return
-errno in error case as suggested by Cedric.
- Added Reviewed-by tags.
Changes from v4 :
- Rebased on latest master branch.
- Added linux header update to kernel v6.2-rc1.
- Merged preview patches (#13-14) into this series.
Changes from v3 :
- Rebased on latest master branch.
- Dropped patch #1 "migration: Remove res_compatible parameter" as
it's not mandatory to this series and needs some further discussion.
- Dropped patch #3 "migration: Block migration comment or code is
wrong" as it has been merged already.
- Addressed overlooked corner case reported by Vladimir in patch #4
"migration: Simplify migration_iteration_run()".
- Dropped patch #5 "vfio/migration: Fix wrong enum usage" as it has
been merged already.
- In patch #12 "vfio/migration: Implement VFIO migration protocol v2":
1. Changed vfio_save_pending() to update res_precopy_only instead of
res_postcopy_only (as VFIO migration doesn’t support postcopy).
2. Moved VFIOMigration->data_buffer allocation to vfio_save_setup()
and its de-allocation to vfio_save_cleanup(), so now it's
allocated when actually used (during migration and only on source
- Addressed Alex's comments:
1. Eliminated code duplication in patch #7 "vfio/migration: Allow
migration without VFIO IOMMU dirty tracking support".
2. Removed redundant initialization of vfio_region_info in patch #10
"vfio/migration: Move migration v1 logic to vfio_migration_init()".
3. Added comment about VFIO_MIG_DATA_BUFFER_SIZE heuristic (and
renamed to VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE).
4. Cast migration structs to their actual types instead of void *.
5. Return -errno and -EBADF instead of -1 in vfio_migration_set_state().
6. Set migration->device_state to new_state even in case of data_fd
out of sync. Although migration will be aborted, setting device
state succeeded so we should reflect that.
7. Renamed VFIO_MIG_PENDING_SIZE to VFIO_MIG_STOP_COPY_SIZE, set it
to 100G and added a comment about the size choice.
8. Changed vfio_save_block() to return -errno on error.
9. Squashed Patch #14 to patch #12.
10. Adjusted migration data buffer size according to MIG_DATA_SIZE
- In preview patch #17 "vfio/migration: Query device data size in
vfio_save_pending()" - changed vfio_save_pending() to report
VFIO_MIG_STOP_COPY_SIZE on any error.
- Added another preview patch "vfio/migration: Optimize
- Added ret value on some traces as suggested by David.
- Added Reviewed-By tags.
Changes from v2 :
- Rebased on top of latest master branch.
- Added relevant patches from Juan's RFC  with minor changes:
1. Added Reviewed-by tag to patch #3 in the RFC.
2. Adjusted patch #6 to work without patch #4 in the RFC.
- Added a new patch "vfio/migration: Fix wrong enum usage" that fixes a
small bug in v1 code. This patch has been sent a few weeks ago  but
wasn't taken yet.
- Patch #2 (vfio/migration: Skip pre-copy if dirty page tracking is not
1. Dropped this patch and replaced it with
"vfio/migration: Allow migration without VFIO IOMMU dirty tracking
The new patch uses a different approach – instead of skipping
pre-copy phase completely, QEMU VFIO code will mark RAM dirty
(instead of kernel). This ensures that current migration behavior
is not changed and SLA is taken into account.
- Patch #4 (vfio/common: Change vfio_devices_all_running_and_saving()
logic to equivalent one):
1. Improved commit message to better explain the change.
- Patch #7 (vfio/migration: Implement VFIO migration protocol v2):
1. Enhanced vfio_migration_set_state() error reporting.
2. In vfio_save_complete_precopy() of v2 protocol - when changing
device state to STOP, set recover state to ERROR instead of STOP as
suggested by Joao.
3. Constify SaveVMHandlers of v2 protocol.
4. Modified trace_vfio_vmstate_change and
to print device state string instead of enum.
5. Replaced qemu_put_buffer_async() with qemu_put_buffer() in
vfio_save_block(), as requested by Juan.
6. Implemented v2 protocol version of vfio_save_pending() as requested
by Juan. Until ioctl to get device state size is added, we just
report some big hard coded value, as agreed in KVM call.
- Patch #9 (vfio/migration: Reset device if setting recover state
1. Enhanced error reporting.
2. Set VFIOMigration->device_state to RUNNING after device reset.
- Patch #11 (docs/devel: Align vfio-migration docs to VFIO migration
1. Adjusted vfio migration documentation to the added
- Added the last patch (which is not for merging yet) that demonstrates
how the new ioctl to get device state size will work once added.
Changes from v1 :
- Split the big patch that replaced v1 with v2 into several patches as
suggested by Joao, to make review easier.
- Change warn_report to warn_report_once when container doesn't support
- Add Reviewed-by tag.
Avihai Horon (12):
linux-headers: Update to v6.2-rc1
vfio/migration: Fix NULL pointer dereference bug
vfio/migration: Allow migration without VFIO IOMMU dirty tracking
migration/qemu-file: Add qemu_file_get_to_fd()
vfio/common: Change vfio_devices_all_running_and_saving() logic to
vfio/migration: Move migration v1 logic to vfio_migration_init()
vfio/migration: Rename functions/structs related to v1 protocol
vfio/migration: Implement VFIO migration protocol v2
vfio/migration: Optimize vfio_save_pending()
vfio/migration: Remove VFIO migration protocol v1
vfio: Alphabetize migration section of VFIO trace-events file
docs/devel: Align VFIO migration docs to v2 protocol
Juan Quintela (1):
migration: No save_live_pending() method uses the QEMUFile parameter
docs/devel/vfio-migration.rst | 68 +-
include/hw/vfio/vfio-common.h | 10 +-
include/migration/register.h | 3 +-
include/standard-headers/drm/drm_fourcc.h | 63 +-
include/standard-headers/linux/ethtool.h | 81 +-
include/standard-headers/linux/fuse.h | 20 +-
.../linux/input-event-codes.h | 4 +
include/standard-headers/linux/pci_regs.h | 2 +
include/standard-headers/linux/virtio_blk.h | 19 +
include/standard-headers/linux/virtio_bt.h | 8 +
include/standard-headers/linux/virtio_net.h | 4 +
linux-headers/asm-arm64/kvm.h | 1 +
linux-headers/asm-generic/hugetlb_encode.h | 26 +-
linux-headers/asm-generic/mman-common.h | 2 +
linux-headers/asm-mips/mman.h | 2 +
linux-headers/asm-riscv/kvm.h | 7 +
linux-headers/asm-x86/kvm.h | 11 +-
linux-headers/linux/kvm.h | 32 +-
linux-headers/linux/psci.h | 14 +
linux-headers/linux/userfaultfd.h | 4 +
linux-headers/linux/vfio.h | 278 ++++++-
migration/qemu-file.h | 1 +
migration/savevm.h | 3 +-
hw/s390x/s390-stattrib.c | 2 +-
hw/vfio/common.c | 41 +-
hw/vfio/migration.c | 748 ++++++------------
migration/block-dirty-bitmap.c | 3 +-
migration/block.c | 2 +-
migration/migration.c | 4 +-
migration/qemu-file.c | 34 +
migration/ram.c | 2 +-
migration/savevm.c | 7 +-
hw/vfio/trace-events | 29 +-
33 files changed, 898 insertions(+), 637 deletions(-)