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Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device
From: |
Yan Zhao |
Subject: |
Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device |
Date: |
Thu, 20 Jun 2019 21:24:05 -0400 |
User-agent: |
Mutt/1.9.4 (2018-02-28) |
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
> >
- [Qemu-devel] [PATCH v4 09/13] vfio: Add load state functions to SaveVMHandlers, (continued)
- [Qemu-devel] [PATCH v4 09/13] vfio: Add load state functions to SaveVMHandlers, Kirti Wankhede, 2019/06/20
- [Qemu-devel] [PATCH v4 10/13] vfio: Add function to get dirty page list, Kirti Wankhede, 2019/06/20
- [Qemu-devel] [PATCH v4 11/13] vfio: Add vfio_listerner_log_sync to mark dirty pages, Kirti Wankhede, 2019/06/20
- [Qemu-devel] [PATCH v4 12/13] vfio: Make vfio-pci device migration capable., Kirti Wankhede, 2019/06/20
- [Qemu-devel] [PATCH v4 13/13] vfio: Add trace events in migration code path, Kirti Wankhede, 2019/06/20
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Yan Zhao, 2019/06/20
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device,
Yan Zhao <=
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Kirti Wankhede, 2019/06/21
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Yan Zhao, 2019/06/21
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Kirti Wankhede, 2019/06/21
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Yan Zhao, 2019/06/21
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Dr. David Alan Gilbert, 2019/06/24
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Yan Zhao, 2019/06/25
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Dr. David Alan Gilbert, 2019/06/28
- Re: [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device, Yan Zhao, 2019/06/28