linux-kernel - Re: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH

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Date:   Mon, 30 Apr 2018 17:33:05 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com>
Cc:     Pierre Morel <pmorel@...ux.vnet.ibm.com>, pasic@...ux.vnet.ibm.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ
 event

On Thu, 26 Apr 2018 15:48:06 +0800
Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com> wrote:

> * Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com> [2018-04-26 15:30:54 +0800]:
> 
> [...]
> 
> > > @@ -179,7 +160,7 @@ static int fsm_irq(struct vfio_ccw_private *private,
> > >  	if (private->io_trigger)
> > >  		eventfd_signal(private->io_trigger, 1);
> > > 
> > > -	return private->state;
> > > +	return VFIO_CCW_STATE_IDLE;  
> > This is not right. For example, if we are in STANDBY state (subch driver
> > is probed, but mdev device is not created), we can not jump to IDLE
> > state.
> >   
> I see my problem, for STANDBY state, we should introduce another event
> callback for VFIO_CCW_EVENT_INTERRUPT. It doesn't make sense to call
> fsm_irq() which tries to signal userspace with interrupt notification
> when mdev is not created yet... So we'd need a separated fix for this
> issue too.

But how do we even get into that situation when we don't have an mdev
yet?