4db52602a6
The optional PRE_COPY states open the saving data transfer FD before
reaching STOP_COPY and allows the device to dirty track internal state
changes with the general idea to reduce the volume of data transferred
in the STOP_COPY stage.
While in PRE_COPY the device remains RUNNING, but the saving FD is open.
Only if the device also supports RUNNING_P2P can it support PRE_COPY_P2P,
which halts P2P transfers while continuing the saving FD.
PRE_COPY, with P2P support, requires the driver to implement 7 new arcs
and exists as an optional FSM branch between RUNNING and STOP_COPY:
RUNNING -> PRE_COPY -> PRE_COPY_P2P -> STOP_COPY
A new ioctl VFIO_MIG_GET_PRECOPY_INFO is provided to allow userspace to
query the progress of the precopy operation in the driver with the idea it
will judge to move to STOP_COPY at least once the initial data set is
transferred, and possibly after the dirty size has shrunk appropriately.
This ioctl is valid only in PRE_COPY states and kernel driver should
return -EINVAL from any other migration state.
Compared to the v1 clarification, STOP_COPY -> PRE_COPY is blocked
and to be defined in future.
We also split the pending_bytes report into the initial and sustaining
values, e.g.: initial_bytes and dirty_bytes.
initial_bytes: Amount of initial precopy data.
dirty_bytes: Device state changes relative to data previously retrieved.
These fields are not required to have any bearing to STOP_COPY phase.
It is recommended to leave PRE_COPY for STOP_COPY only after the
initial_bytes field reaches zero. Leaving PRE_COPY earlier might make
things slower.
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20221206083438.37807-3-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rv | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| ufs | ||
| vdso | ||
| video | ||
| xen | ||