linux-kernel - Re: [PATCH 07/10] vfio: ccw: Introduce the INIT event

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Date:   Mon, 30 Apr 2018 17:39:10 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Pierre Morel <pmorel@...ux.vnet.ibm.com>
Cc:     pasic@...ux.vnet.ibm.com, bjsdjshi@...ux.vnet.ibm.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 07/10] vfio: ccw: Introduce the INIT event

On Thu, 19 Apr 2018 16:48:10 +0200
Pierre Morel <pmorel@...ux.vnet.ibm.com> wrote:

> The VFIO_CCW_EVENT_INIT event allows to export the initial state
> into the FSM.

I don't know, that feels a bit unintuitive to me. I would naively
expect initialization to be done _before_ we activate processing via
the state machine.

> 
> Signed-off-by: Pierre Morel <pmorel@...ux.vnet.ibm.com>
> ---
>  drivers/s390/cio/vfio_ccw_drv.c     | 26 +++++++++++---------------
>  drivers/s390/cio/vfio_ccw_fsm.c     | 21 +++++++++++++++++++++
>  drivers/s390/cio/vfio_ccw_ops.c     | 11 -----------
>  drivers/s390/cio/vfio_ccw_private.h |  1 +
>  4 files changed, 33 insertions(+), 26 deletions(-)

>  /*
>   * Device statemachine
>   */
>  fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
>  	[VFIO_CCW_STATE_NOT_OPER] = {
> +		[VFIO_CCW_EVENT_INIT]		= fsm_init,
>  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_nop,
>  		[VFIO_CCW_EVENT_SSCH_REQ]	= fsm_io_error,
>  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_disabled_irq,
>  		[VFIO_CCW_EVENT_SCH_EVENT]	= fsm_nop,
>  	},
>  	[VFIO_CCW_STATE_STANDBY] = {
> +		[VFIO_CCW_EVENT_INIT]		= fsm_nop,
>  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
>  		[VFIO_CCW_EVENT_SSCH_REQ]	= fsm_io_error,
>  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
>  		[VFIO_CCW_EVENT_SCH_EVENT]	= fsm_sch_event,
>  	},
>  	[VFIO_CCW_STATE_IDLE] = {
> +		[VFIO_CCW_EVENT_INIT]		= fsm_nop,
>  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
>  		[VFIO_CCW_EVENT_SSCH_REQ]	= fsm_io_request,
>  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
>  		[VFIO_CCW_EVENT_SCH_EVENT]	= fsm_sch_event,
>  	},
>  	[VFIO_CCW_STATE_BOXED] = {
> +		[VFIO_CCW_EVENT_INIT]		= fsm_nop,
>  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
>  		[VFIO_CCW_EVENT_SSCH_REQ]	= fsm_io_busy,
>  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
>  		[VFIO_CCW_EVENT_SCH_EVENT]	= fsm_sch_event,
>  	},
>  	[VFIO_CCW_STATE_BUSY] = {
> +		[VFIO_CCW_EVENT_INIT]		= fsm_nop,
>  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
>  		[VFIO_CCW_EVENT_SSCH_REQ]	= fsm_io_busy,
>  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,

...especially as you only call it if in the NOT_OPER state. Why should
this event be generated in any case but in the very beginning?