Re: [PATCH v7 11/15] s390/vfio-ap: Transition device migration state to STOP

["Jason J. Herne" <jjherne@linux.ibm.com>]

On 8/7/26 6:18 PM, Anthony Krowiak wrote:
> Typically at this point, interrupt processing for the device, DMA and other
> changes to the device's external state must be prohibited. For VFIO AP,
> there is no physical DMA device virtualized by the vfio-ap device . It
> merely manages the guest's AP configuration that identifies the devices
> passed through to the guest, but does not have access to any of them. Those
> AP devices are passed through and controlled exclusively by the SIE program

SIE is an instruction, not a program. It might be clearer to say:
pass-through AP devices are controlled by the hardware.

I'm not sure there is much benefit to having this as a separate patch at 
all. You could simply roll this into the patch where this logic is 
originally constructed and skip this patch entirely.

> used to start the guest. There  only thing to do at this point is return
> NULL to the caller since the file streams and associated data will get
> cleaned up as a result of the VFIO migration framework releasing the files.
> 
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
> ---
>   drivers/s390/crypto/vfio_ap_migration.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
> index 4dd7373c3d9d..30160e3ddded 100644
> --- a/drivers/s390/crypto/vfio_ap_migration.c
> +++ b/drivers/s390/crypto/vfio_ap_migration.c
> @@ -1511,12 +1511,17 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
>   		return filp;
>   	}
>   
> +	/*
> +	 * Terminates the data transfer session of the vfio-ap device state
> +	 * between the source and target hosts. Since the vfio-ap device does
> +	 * not virtualize a DMA device, there is no internal device state to
> +	 * incorporate into the vfio-ap device on the target.
> +	 */
>   	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
>   	     new_state == VFIO_DEVICE_STATE_STOP) ||
>   	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
>   	     new_state == VFIO_DEVICE_STATE_STOP)) {
> -		/* TODO */
> -		return ERR_PTR(-EOPNOTSUPP);
> +		return NULL;
>   	}
>   
>   	if ((cur_state == VFIO_DEVICE_STATE_STOP &&