Re: [PATCH v6 09/10] hisi_acc_vfio_pci: Add support for VFIO live migration

Jason Gunthorpe
2022-02-28T23:47:26Z

On Mon, Feb 28, 2022 at 02:20:34PM -0700, Alex Williamson wrote:

> > Unless you think we should block it.
>
> What's the meaning of initial_bytes and dirty_bytes while in
> STOP_COPY?

Same as during pre-copy - both numbers are the bytes remaining to be
read() from the FD in each bucket. They should continue to decline as
read() progresses regardless of what state the data_fd is in.

The only special thing about STOP_COPY is that dirty_bytes should not
increase as the device should not be generating new dirty data.

How about:

* Drivers should attempt to return estimates so that initial_bytes +
* dirty_bytes matches the amount of data an immediate transition to STOP_COPY
* will require to be streamed. While in STOP_COPY the initial_bytes
* and dirty_bytes should continue to be decrease as the data_fd
* progresses streaming out the data.

Remove the 'in the precopy phase' from the first sentance

Adjust the last paragraph as:

+ * returning readable. ENOMSG may not be returned in STOP_COPY. Support
+ * for this ioctl is required when VFIO_MIGRATION_PRE_COPY is set.

Jason