From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ
 event
Date: Wed, 2 May 2018 10:22:17 +0200
Message-ID: <20180502102217.702870af.cohuck@redhat.com>
References: <1524149293-12658-1-git-send-email-pmorel@linux.vnet.ibm.com>
        <1524149293-12658-5-git-send-email-pmorel@linux.vnet.ibm.com>
        <20180426073053.GZ12194@bjsdjshi@linux.vnet.ibm.com>
        <20180426074806.GB12194@bjsdjshi@linux.vnet.ibm.com>
        <20180430173305.632faa80.cohuck@redhat.com>
        <20180502074622.GV5428@bjsdjshi@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20180502074622.GV5428@bjsdjshi@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Archive: <https://lore.kernel.org/kvm/>
List-Post: <mailto:kvm@vger.kernel.org>
To: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Cc: Pierre Morel <pmorel@linux.vnet.ibm.com>, pasic@linux.vnet.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org
List-ID: <linux-s390.vger.kernel.org>

On Wed, 2 May 2018 15:46:22 +0800
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> * Cornelia Huck <cohuck@redhat.com> [2018-04-30 17:33:05 +0200]:
> 
> > On Thu, 26 Apr 2018 15:48:06 +0800
> > Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
> >   
> > > * Dong Jia Shi <bjsdjshi@linux.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?
> >   
> We cann't... So let's assign fsm_nop() as the interrupt callback for
> STANDBY state?

Either that, or have a special fsm_should_not_happen() function that
can pop out a trace message and then continue to do nothing.