Re: [PATCH V1 0/5] vfio virtual address update

[Steven Sistare <steven.sistare@oracle.com>]

On 1/5/2021 10:36 AM, Steve Sistare wrote:
> Add interfaces that allow the underlying memory object of an iova range
> to be mapped to a new virtual address in the host process:
> 
>   - VFIO_DMA_UNMAP_FLAG_SUSPEND for VFIO_IOMMU_UNMAP_DMA
>   - VFIO_DMA_MAP_FLAG_RESUME flag for VFIO_IOMMU_MAP_DMA
>   - VFIO_SUSPEND extension for VFIO_CHECK_EXTENSION
> 
> The suspend interface blocks vfio translation of host virtual addresses in
> a range, but DMA to already-mapped pages continues.  The resume interface
> records the new base VA and resumes translation.  The implementation
> supports iommu type1 and mediated devices.
> 
> This functionality is necessary for live update, in which a host process
> such as qemu exec's an updated version of itself, while preserving its
> guest and vfio devices.  The process suspends vfio VA translation, exec's
> its new self, mmap's the memory object(s) underlying vfio object, and
> resumes VA translation.  For a working example that uses these new
> interfaces, see the QEMU patch series "[PATCH V2] Live Update".
> 
> Patch 1 modifies the iova rbtree to allow iteration over ranges with gaps,
>   without deleting each entry.  This is required by patch 4.
> Patch 2 adds an option to unmap all ranges, which simplifies userland code.
> Patch 3 adds an interface to detect if an iommu_group has a valid container,
>   which patch 5 uses to release a blocked thread if a container is closed.
> Patch 4 implements the new ioctl's.
> Patch 5 adds blocking to complete the implementation .
> 
> Steve Sistare (5):
>   vfio: maintain dma_list order
>   vfio: option to unmap all
>   vfio: detect closed container
>   vfio: VA suspend interface
>   vfio: block during VA suspend
> 
>  drivers/vfio/vfio.c             |  12 ++++
>  drivers/vfio/vfio_iommu_type1.c | 122 ++++++++++++++++++++++++++++++++++------
>  include/linux/vfio.h            |   1 +
>  include/uapi/linux/vfio.h       |  19 ++++++-
>  4 files changed, 135 insertions(+), 19 deletions(-)
> 

Hi Alex,
  I can send a patch V2 for review if you weigh in on the following:

* preferred interface for unmap-all (patch 2)
* name of the suspend and resume flags (patch 4)
* is vfio_iommu_contained() acceptable, or is a new backend interface needed? (patch 5)

- Steve