[vfio-users] location of regions VFIO_REGION_TYPE_MIGRATION/VFIO_REGION_SUBTYPE_MIGRATION

[Auger Eric]

Hi Thanos,

On 10/2/20 2:54 PM, Thanos Makatos wrote:
> According to linux/include/uapi/linux/vfio.h, for a device to support migration
> it must provide a VFIO capability of type VFIO_REGION_INFO_CAP_TYPE and set
> .type/.subtype to VFIO_REGION_TYPE_MIGRATION/VFIO_REGION_TYPE_MIGRATION.
> 
> What confuses me is the following:
> 
> "The structure vfio_device_migration_info is placed at the 0th offset of
> the VFIO_REGION_SUBTYPE_MIGRATION region to get and set VFIO device related
> migration information."
> 
> Where do regions VFIO_REGION_TYPE_MIGRATION and VFIO_REGION_SUBTYPE_MIGRATION
> live on the device's address space? Is just like any other region, except that
> in the case of a PCI device it's index must be equal to, or larger than,
> VFIO_PCI_NUM_REGIONS, and set arbitrarily by the device implementation? If
> so, then I suppose this index must appear in struct vfio_device_info.num_regions?

You need to call VFIO_DEVICE_GET_REGION_INFO with the region
type/subtype. The index of the region is stored in struct
vfio_region_info index.

Thanks

Eric
> 
> 
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