Re: [PATCH v16 Kernel 1/7] vfio: KABI for migration interface for device state

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 25 Mar 2020 01:02:33 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> - Defined MIGRATION region type and sub-type.
> 
> - Defined vfio_device_migration_info structure which will be placed at the
>   0th offset of migration region to get/set VFIO device related
>   information. Defined members of structure and usage on read/write access.
> 
> - Defined device states and state transition details.
> 
> - Defined sequence to be followed while saving and resuming VFIO device.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  include/uapi/linux/vfio.h | 228 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 228 insertions(+)

(...)

> +struct vfio_device_migration_info {
> +	__u32 device_state;         /* VFIO device state */
> +#define VFIO_DEVICE_STATE_STOP      (0)
> +#define VFIO_DEVICE_STATE_RUNNING   (1 << 0)
> +#define VFIO_DEVICE_STATE_SAVING    (1 << 1)
> +#define VFIO_DEVICE_STATE_RESUMING  (1 << 2)
> +#define VFIO_DEVICE_STATE_MASK      (VFIO_DEVICE_STATE_RUNNING | \
> +				     VFIO_DEVICE_STATE_SAVING |  \
> +				     VFIO_DEVICE_STATE_RESUMING)
> +
> +#define VFIO_DEVICE_STATE_VALID(state) \
> +	(state & VFIO_DEVICE_STATE_RESUMING ? \
> +	(state & VFIO_DEVICE_STATE_MASK) == VFIO_DEVICE_STATE_RESUMING : 1)
> +
> +#define VFIO_DEVICE_STATE_IS_ERROR(state) \
> +	((state & VFIO_DEVICE_STATE_MASK) == (VFIO_DEVICE_STATE_SAVING | \
> +					      VFIO_DEVICE_STATE_RESUMING))
> +
> +#define VFIO_DEVICE_STATE_SET_ERROR(state) \
> +	((state & ~VFIO_DEVICE_STATE_MASK) | VFIO_DEVICE_SATE_SAVING | \
> +					     VFIO_DEVICE_STATE_RESUMING)
> +
> +	__u32 reserved;
> +	__u64 pending_bytes;
> +	__u64 data_offset;
> +	__u64 data_size;
> +} __attribute__((packed));

The 'packed' should not even be needed, I think?

> +
>  /*
>   * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
>   * which allows direct access to non-MSIX registers which happened to be within

Generally, this looks sane to me; however, we should really have
something under Documentation/ in the long run that describes how this
works, so that you can find out about the protocol without having to
dig through headers.