On Fri, Jun 21, 2019 at 08:25:18AM +0800, Yan Zhao wrote: > On Thu, Jun 20, 2019 at 10:37:28PM +0800, Kirti Wankhede wrote: > > Add migration support for VFIO device > > > > This Patch set include patches as below: > > - Define KABI for VFIO device for migration support. > > - Added save and restore functions for PCI configuration space > > - Generic migration functionality for VFIO device. > > * This patch set adds functionality only for PCI devices, but can be > > extended to other VFIO devices. > > * Added all the basic functions required for pre-copy, stop-and-copy and > > resume phases of migration. > > * Added state change notifier and from that notifier function, VFIO > > device's state changed is conveyed to VFIO device driver. > > * During save setup phase and resume/load setup phase, migration region > > is queried and is used to read/write VFIO device data. > > * .save_live_pending and .save_live_iterate are implemented to use QEMU's > > functionality of iteration during pre-copy phase. > > * In .save_live_complete_precopy, that is in stop-and-copy phase, > > iteration to read data from VFIO device driver is implemented till > > pending > > bytes returned by driver are not zero. > > * Added function to get dirty pages bitmap for the pages which are used by > > driver. > > - Add vfio_listerner_log_sync to mark dirty pages. > > - Make VFIO PCI device migration capable. If migration region is not > > provided by > > driver, migration is blocked. > > > > Below is the flow of state change for live migration where states in > > brackets > > represent VM state, migration state and VFIO device state as: > > (VM state, MIGRATION_STATUS, VFIO_DEVICE_STATE) > > > > Live migration save path: > > QEMU normal running state > > (RUNNING, _NONE, _RUNNING) > > | > > migrate_init spawns migration_thread. > > (RUNNING, _SETUP, _RUNNING|_SAVING) > > Migration thread then calls each device's .save_setup() > > | > > (RUNNING, _ACTIVE, _RUNNING|_SAVING) > > If device is active, get pending bytes by .save_live_pending() > > if pending bytes >= threshold_size, call save_live_iterate() > > Data of VFIO device for pre-copy phase is copied. > > Iterate till pending bytes converge and are less than threshold > > | > > On migration completion, vCPUs stops and calls > > .save_live_complete_precopy > > for each active device. VFIO device is then transitioned in > > _SAVING state. > > (FINISH_MIGRATE, _DEVICE, _SAVING) > > For VFIO device, iterate in .save_live_complete_precopy until > > pending data is 0. > > (FINISH_MIGRATE, _DEVICE, _STOPPED) > > I suggest we also register to VMStateDescription, whose .pre_save > handler would get called after .save_live_complete_precopy in pre-copy > only case, and will called before .save_live_iterate in post-copy > enabled case. > In the .pre_save handler, we can save all device state which must be > copied after device stop in source vm and before device start in target vm. > hi to better describe this idea:
in pre-copy only case, the flow is start migration --> .save_live_iterate (several round) -> stop source vm --> .save_live_complete_precopy --> .pre_save -->start target vm -->migration complete in post-copy enabled case, the flow is start migration --> .save_live_iterate (several round) --> start post copy --> stop source vm --> .pre_save --> start target vm --> .save_live_iterate (several round) -->migration complete Therefore, we should put saving of device state in .pre_save interface rather than in .save_live_complete_precopy. The device state includes pci config data, page tables, register state, etc. The .save_live_iterate and .save_live_complete_precopy should only deal with saving dirty memory. I know current implementation does not support post-copy. but at least it should not require huge change when we decide to enable it in future. Thanks Yan > > | > > (FINISH_MIGRATE, _COMPLETED, STOPPED) > > Migraton thread schedule cleanup bottom half and exit > > > > Live migration resume path: > > Incomming migration calls .load_setup for each device > > (RESTORE_VM, _ACTIVE, STOPPED) > > | > > For each device, .load_state is called for that device section data > > | > > At the end, called .load_cleanup for each device and vCPUs are started. > > | > > (RUNNING, _NONE, _RUNNING) > > > > Note that: > > - Migration post copy is not supported. > > > > v3 -> v4: > > - Added one more bit for _RESUMING flag to be set explicitly. > > - data_offset field is read-only for user space application. > > - data_size is read for every iteration before reading data from migration, > > that > > is removed assumption that data will be till end of migration region. > > - If vendor driver supports mappable sparsed region, map those region during > > setup state of save/load, similarly unmap those from cleanup routines. > > - Handles race condition that causes data corruption in migration region > > during > > save device state by adding mutex and serialiaing save_buffer and > > get_dirty_pages routines. > > - Skip called get_dirty_pages routine for mapped MMIO region of device. > > - Added trace events. > > - Splitted into multiple functional patches. > > > > v2 -> v3: > > - Removed enum of VFIO device states. Defined VFIO device state with 2 bits. > > - Re-structured vfio_device_migration_info to keep it minimal and defined > > action > > on read and write access on its members. > > > > v1 -> v2: > > - Defined MIGRATION region type and sub-type which should be used with > > region > > type capability. > > - Re-structured vfio_device_migration_info. This structure will be placed > > at 0th > > offset of migration region. > > - Replaced ioctl with read/write for trapped part of migration region. > > - Added both type of access support, trapped or mmapped, for data section > > of the > > region. > > - Moved PCI device functions to pci file. > > - Added iteration to get dirty page bitmap until bitmap for all requested > > pages > > are copied. > > > > Thanks, > > Kirti > > > > > > Kirti Wankhede (13): > > vfio: KABI for migration interface > > vfio: Add function to unmap VFIO region > > vfio: Add save and load functions for VFIO PCI devices > > vfio: Add migration region initialization and finalize function > > vfio: Add VM state change handler to know state of VM > > vfio: Add migration state change notifier > > vfio: Register SaveVMHandlers for VFIO device > > vfio: Add save state functions to SaveVMHandlers > > vfio: Add load state functions to SaveVMHandlers > > vfio: Add function to get dirty page list > > vfio: Add vfio_listerner_log_sync to mark dirty pages > > vfio: Make vfio-pci device migration capable. > > vfio: Add trace events in migration code path > > > > hw/vfio/Makefile.objs | 2 +- > > hw/vfio/common.c | 55 +++ > > hw/vfio/migration.c | 815 > > ++++++++++++++++++++++++++++++++++++++++++ > > hw/vfio/pci.c | 126 ++++++- > > hw/vfio/pci.h | 29 ++ > > hw/vfio/trace-events | 19 + > > include/hw/vfio/vfio-common.h | 22 ++ > > linux-headers/linux/vfio.h | 71 ++++ > > 8 files changed, 1132 insertions(+), 7 deletions(-) > > create mode 100644 hw/vfio/migration.c > > > > -- > > 2.7.0 > >
