Re: [RFC PATCH v1 02/10] vfio-ccw: Register a chp_event callback for vfio-ccw

[Cornelia Huck <cohuck@redhat.com>]

On Fri, 15 Nov 2019 03:56:12 +0100
Eric Farman <farman@linux.ibm.com> wrote:

> From: Farhan Ali <alifm@linux.ibm.com>
> 
> Register the chp_event callback to receive channel path related
> events for the subchannels managed by vfio-ccw.
> 
> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
> 
> Notes:
>     v0->v1: [EF]
>      - Add s390dbf trace
> 
>  drivers/s390/cio/vfio_ccw_drv.c | 44 +++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
> index 91989269faf1..05da1facee60 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -19,6 +19,7 @@
>  
>  #include <asm/isc.h>
>  
> +#include "chp.h"
>  #include "ioasm.h"
>  #include "css.h"
>  #include "vfio_ccw_private.h"
> @@ -257,6 +258,48 @@ static int vfio_ccw_sch_event(struct subchannel *sch, int process)
>  	return rc;
>  }
>  
> +static int vfio_ccw_chp_event(struct subchannel *sch,
> +			      struct chp_link *link, int event)
> +{
> +	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
> +	int mask = chp_ssd_get_mask(&sch->ssd_info, link);
> +	int retry = 255;
> +
> +	if (!private || !mask)
> +		return 0;
> +
> +	if (cio_update_schib(sch))
> +		return -ENODEV;

It seems this return code is only checked by the common I/O layer for
the _OFFLINE case; still, it's probably not a bad idea, even though it
is different from what the vanilla I/O subchannel driver does.

> +
> +	VFIO_CCW_MSG_EVENT(2, "%pUl (%x.%x.%04x): mask=0x%x event=%d\n",
> +			   mdev_uuid(private->mdev), sch->schid.cssid,
> +			   sch->schid.ssid, sch->schid.sch_no,
> +			   mask, event);

If you log only here, you're missing the case above.

> +
> +	switch (event) {
> +	case CHP_VARY_OFF:
> +		/* Path logically turned off */
> +		sch->opm &= ~mask;
> +		sch->lpm &= ~mask;
> +		break;
> +	case CHP_OFFLINE:
> +		/* Path is gone */
> +		cio_cancel_halt_clear(sch, &retry);
> +		break;
> +	case CHP_VARY_ON:
> +		/* Path logically turned on */
> +		sch->opm |= mask;
> +		sch->lpm |= mask;
> +		break;
> +	case CHP_ONLINE:
> +		/* Path became available */
> +		sch->lpm |= mask & sch->opm;
> +		break;
> +	}

Looks sane as the first round.

> +
> +	return 0;
> +}
> +
>  static struct css_device_id vfio_ccw_sch_ids[] = {
>  	{ .match_flags = 0x1, .type = SUBCHANNEL_TYPE_IO, },
>  	{ /* end of list */ },
> @@ -274,6 +317,7 @@ static struct css_driver vfio_ccw_sch_driver = {
>  	.remove = vfio_ccw_sch_remove,
>  	.shutdown = vfio_ccw_sch_shutdown,
>  	.sch_event = vfio_ccw_sch_event,
> +	.chp_event = vfio_ccw_chp_event,
>  };
>  
>  static int __init vfio_ccw_debug_init(void)