-
Notifications
You must be signed in to change notification settings - Fork 0
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
vfio: Extend the device migration protocol with PRE_COPY
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>
- Loading branch information
Jason Gunthorpe
authored and
Alex Williamson
committed
Dec 6, 2022
1 parent
c943a93
commit 4db5260
Showing
2 changed files
with
191 additions
and
6 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters