Re: [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device

[Cornelia Huck]

On Wed, 23 Sep 2020 04:54:09 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> Define flags to be used as delimeter in migration file stream.
> Added .save_setup and .save_cleanup functions. Mapped & unmapped migration
> region from these functions at source during saving or pre-copy phase.
> Set VFIO device state depending on VM's state. During live migration, VM is
> running when .save_setup is called, _SAVING | _RUNNING state is set for VFIO
> device. During save-restore, VM is paused, _SAVING state is set for VFIO 
> device.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  hw/vfio/migration.c  | 91 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/vfio/trace-events |  2 ++
>  2 files changed, 93 insertions(+)
> 

(...)

> +/*
> + * Flags used as delimiter:
> + * 0xffffffff => MSB 32-bit all 1s
> + * 0xef10     => emulated (virtual) function IO

Where is this value coming from?

> + * 0x0000     => 16-bits reserved for flags
> + */
> +#define VFIO_MIG_FLAG_END_OF_STATE      (0xffffffffef100001ULL)
> +#define VFIO_MIG_FLAG_DEV_CONFIG_STATE  (0xffffffffef100002ULL)
> +#define VFIO_MIG_FLAG_DEV_SETUP_STATE   (0xffffffffef100003ULL)
> +#define VFIO_MIG_FLAG_DEV_DATA_STATE    (0xffffffffef100004ULL)

I think we need some more documentation what these values mean and how
they are used. From reading ahead a bit, it seems there is always
supposed to be a pair of DEV_*_STATE and END_OF_STATE framing some kind
of data?

(...)