Clément, Yi Liu,
On 10/17/25 10:22, Zhenzhong Duan wrote:
If a VFIO device in guest switches from IOMMU domain to block domain,
vtd_address_space_unmap() is called to unmap whole address space.
If that happens during migration, migration fails with legacy VFIO
backend as below:
Status: failed (vfio_container_dma_unmap(0x561bbbd92d90, 0x100000000000,
0x100000000000) = -7 (Argument list too long))
Because legacy VFIO limits maximum bitmap size to 256MB which maps to 8TB on
4K page system, when 16TB sized UNMAP notification is sent, unmap_bitmap
ioctl fails.
Fix it by iterating over DMAMap list to unmap each range with active mapping
when migration is active. If migration is not active, unmapping the whole
address space in one go is optimal.
There is no such limitation with iommufd backend, but it's still not optimal
to allocate large bitmap, e.g., there may be large hole between IOVA ranges,
allocating large bitmap and dirty tracking on the hole is time consuming and
useless work.
Signed-off-by: Zhenzhong Duan <[email protected]>
Tested-by: Giovannio Cabiddu <[email protected]>
---
hw/i386/intel_iommu.c | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
Could you ack this change please ?
Thanks,
C.
