[PATCH V1 0/5] vfio virtual address update

Steve Sistare
2021-01-05T16:05:07Z

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(-)

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1.8.3.1