When synchronizing dirty bitmap from kernel VFIO we do it in a
per-iova-range fashion and we allocate the userspace bitmap for each of the
ioctl. This patch introduces `struct VFIODMARange` to describe a range of
the given DMA mapping with respect to a VFIO_IOMMU_MAP_DMA operation, and
make the bitmap cache of this range be persistent so that we don't need to
g_try_malloc0() every time. Note that the new structure is almost a copy of
`struct vfio_iommu_type1_dma_map` but only internally used by QEMU.
More importantly, the cached per-iova-range dirty bitmap will be further
used when we want to add support for the CLEAR_BITMAP and this cached
bitmap will be used to guarantee we don't clear any unknown dirty bits
otherwise that can be a severe data loss issue for migration code.
It's pretty intuitive to maintain a bitmap per container since we perform
log_sync at this granule. But I don't know how to deal with things like
memory hot-{un}plug, sparse DMA mappings, etc. Suggestions welcome.
* yet something to-do:
- can't work with guest viommu
- no locks
- etc
[ The idea and even the commit message are largely inherited from kvm side.
See commit 9f4bf4baa8b820c7930e23c9566c9493db7e1d25. ]
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Kunkun Jiang <jinagkunkun@huawei.com>
