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Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device |
Date: |
Thu, 11 Jul 2019 17:23:15 +0100 |
User-agent: |
Mutt/1.12.0 (2019-05-25) |
* Yan Zhao (address@hidden) wrote:
> On Thu, Jul 11, 2019 at 06:50:12PM +0800, Dr. David Alan Gilbert wrote:
> > * Yan Zhao (address@hidden) wrote:
> > > Hi Kirti,
> > > There are still unaddressed comments to your patches v4.
> > > Would you mind addressing them?
> > >
> > > 1. should we register two migration interfaces simultaneously
> > > (https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg04750.html)
> >
> > Please don't do this.
> > As far as I'm aware we currently only have one device that does that
> > (vmxnet3) and a patch has just been posted that fixes/removes that.
> >
> > Dave
> >
> hi Dave,
> Thanks for notifying this. but if we want to support postcopy in future,
> after device stops, what interface could we use to transfer data of
> device state only?
> for postcopy, when source device stops, we need to transfer only
> necessary device state to target vm before target vm starts, and we
> don't want to transfer device memory as we'll do that after target vm
> resuming.
Hmm ok, lets see; that's got to happen in the call to:
qemu_savevm_state_complete_precopy(fb, false, false);
that's made from postcopy_start.
(the false's are iterable_only and inactivate_disks)
and at that time I believe the state is POSTCOPY_ACTIVE, so in_postcopy
is true.
If you're doing postcopy, then you'll probably define a has_postcopy()
function, so qemu_savevm_state_complete_precopy will skip the
save_live_complete_precopy call from it's loop for at least two of the
reasons in it's big if.
So you're right; you need the VMSD for this to happen in the second
loop in qemu_savevm_state_complete_precopy. Hmm.
Now, what worries me, and I don't know the answer, is how the section
header for the vmstate and the section header for an iteration look
on the stream; how are they different?
Dave
> Thanks
> Yan
>
> > > 2. in each save iteration, how much data is to be saved
> > > (https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg04683.html)
> > > 3. do we need extra interface to get data for device state only
> > > (https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg04812.html)
> > > 4. definition of dirty page copied_pfn
> > > (https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg05592.html)
> > >
> > > Also, I'm glad to see that you updated code by following my comments
> > > below,
> > > but please don't forget to reply my comments next time:)
> > > https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg05357.html
> > > https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg06454.html
> > >
> > > Thanks
> > > Yan
> > >
> > > On Tue, Jul 09, 2019 at 05:49:07PM +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)
> > > > |
> > > > (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.
> > > >
> > > > v6 -> v7:
> > > > - Fix build failures.
> > > >
> > > > v5 -> v6:
> > > > - Fix build failure.
> > > >
> > > > v4 -> v5:
> > > > - Added decriptive comment about the sequence of access of members of
> > > > structure
> > > > vfio_device_migration_info to be followed based on Alex's suggestion
> > > > - Updated get dirty pages sequence.
> > > > - As per Cornelia Huck's suggestion, added callbacks to VFIODeviceOps to
> > > > get_object, save_config and load_config.
> > > > - Fixed multiple nit picks.
> > > > - Tested live migration with multiple vfio device assigned to a VM.
> > > >
> > > > 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 vfio_get_object callback to VFIODeviceOps
> > > > 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.
> > > >
> > > > hw/vfio/Makefile.objs | 2 +-
> > > > hw/vfio/common.c | 55 +++
> > > > hw/vfio/migration.c | 874
> > > > ++++++++++++++++++++++++++++++++++++++++++
> > > > hw/vfio/pci.c | 137 ++++++-
> > > > hw/vfio/trace-events | 19 +
> > > > include/hw/vfio/vfio-common.h | 25 ++
> > > > linux-headers/linux/vfio.h | 166 ++++++++
> > > > 7 files changed, 1271 insertions(+), 7 deletions(-)
> > > > create mode 100644 hw/vfio/migration.c
> > > >
> > > > --
> > > > 2.7.0
> > > >
> > --
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
[Qemu-devel] [PATCH v7 12/13] vfio: Add vfio_listerner_log_sync to mark dirty pages, Kirti Wankhede, 2019/07/09
[Qemu-devel] [PATCH v7 13/13] vfio: Make vfio-pci device migration capable., Kirti Wankhede, 2019/07/09
Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Yan Zhao, 2019/07/10
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Dr. David Alan Gilbert, 2019/07/11
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Yan Zhao, 2019/07/11
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Kirti Wankhede, 2019/07/11
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Yan Zhao, 2019/07/11
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Kirti Wankhede, 2019/07/18
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Yan Zhao, 2019/07/18
- Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Dr. David Alan Gilbert, 2019/07/24
Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Dr. David Alan Gilbert, 2019/07/12
Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Yan Zhao, 2019/07/14
Re: [Qemu-devel] [PATCH v7 00/13] Add migration support for VFIO device, Yan Zhao, 2019/07/11