Re: [PATCH v3 00/13] vfio/migration: Device dirty page tracking

[Alex Williamson <alex.williamson@redhat.com>]

On Sat,  4 Mar 2023 01:43:30 +0000
Joao Martins <joao.m.martins@oracle.com> wrote:

> Hey,
> 
> Presented herewith a series based on the basic VFIO migration protocol v2
> implementation [1].
> 
> It is split from its parent series[5] to solely focus on device dirty
> page tracking. Device dirty page tracking allows the VFIO device to
> record its DMAs and report them back when needed. This is part of VFIO
> migration and is used during pre-copy phase of migration to track the
> RAM pages that the device has written to and mark those pages dirty, so
> they can later be re-sent to target.
> 
> Device dirty page tracking uses the DMA logging uAPI to discover device
> capabilities, to start and stop tracking, and to get dirty page bitmap
> report. Extra details and uAPI definition can be found here [3].
> 
> Device dirty page tracking operates in VFIOContainer scope. I.e., When
> dirty tracking is started, stopped or dirty page report is queried, all
> devices within a VFIOContainer are iterated and for each of them device
> dirty page tracking is started, stopped or dirty page report is queried,
> respectively.
> 
> Device dirty page tracking is used only if all devices within a
> VFIOContainer support it. Otherwise, VFIO IOMMU dirty page tracking is
> used, and if that is not supported as well, memory is perpetually marked
> dirty by QEMU. Note that since VFIO IOMMU dirty page tracking has no HW
> support, the last two usually have the same effect of perpetually
> marking all pages dirty.
> 
> Normally, when asked to start dirty tracking, all the currently DMA
> mapped ranges are tracked by device dirty page tracking. If using a
> vIOMMU we block live migration. It's temporary and a separate series is
> going to add support for it. Thus this series focus on getting the
> ground work first.
> 
> The series is organized as follows:
> 
> - Patches 1-7: Fix bugs and do some preparatory work required prior to
>   adding device dirty page tracking.
> - Patches 8-10: Implement device dirty page tracking.
> - Patch 11: Blocks live migration with vIOMMU.
> - Patches 12-13 enable device dirty page tracking and document it.
> 
> Comments, improvements as usual appreciated.

Still some CI failures:

https://gitlab.com/alex.williamson/qemu/-/pipelines/796657474

The docker failures are normal, afaict the rest are not.  Thanks,

Alex