Re: [PATCH 3/3] vfio-ccw: add handling for asnyc channel instructions

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 28 Nov 2018 10:55:11 -0500
Farhan Ali <alifm@linux.ibm.com> wrote:

> On 11/28/2018 10:35 AM, Cornelia Huck wrote:

> > I hacked up the following (still untested):
> > 
> >  From e771c8dc5abbfbd19688b452096bab9d032e0df5 Mon Sep 17 00:00:00 2001
> > From: Cornelia Huck <cohuck@redhat.com>
> > Date: Wed, 28 Nov 2018 16:30:51 +0100
> > Subject: [PATCH] vfio-ccw: make it safe to access channel programs
> > 
> > When we get a solicited interrupt, the start function may have
> > been cleared by a csch, but we still have a channel program
> > structure allocated. Make it safe to call the cp accessors in
> > any case, so we can call them unconditionally.
> > 
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> >   drivers/s390/cio/vfio_ccw_cp.c  | 9 ++++++++-
> >   drivers/s390/cio/vfio_ccw_cp.h  | 2 ++
> >   drivers/s390/cio/vfio_ccw_drv.c | 3 +--
> >   3 files changed, 11 insertions(+), 3 deletions(-)

Hm, this one seems to have fallen through the cracks; but it still does
look useful, especially if we want to allow concurrent handling of
channel operations.

> > 
> > diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> > index 70a006ba4d05..35f87514276b 100644
> > --- a/drivers/s390/cio/vfio_ccw_cp.c
> > +++ b/drivers/s390/cio/vfio_ccw_cp.c
> > @@ -335,6 +335,7 @@ static void cp_unpin_free(struct channel_program *cp)
> >   	struct ccwchain *chain, *temp;
> >   	int i;
> >   
> > +	cp->initialized = false;
> >   	list_for_each_entry_safe(chain, temp, &cp->ccwchain_list, next) {
> >   		for (i = 0; i < chain->ch_len; i++) {
> >   			pfn_array_table_unpin_free(chain->ch_pat + i,
> > @@ -701,6 +702,8 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
> >   	 */
> >   	cp->orb.cmd.c64 = 1;
> >   
> > +	cp->initialized = true;
> > +
> >   	return ret;
> >   }
> >   
> > @@ -715,7 +718,8 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
> >    */
> >   void cp_free(struct channel_program *cp)
> >   {
> > -	cp_unpin_free(cp);
> > +	if (cp->initialized)
> > +		cp_unpin_free(cp);
> >   }
> >   
> >   /**
> > @@ -831,6 +835,9 @@ void cp_update_scsw(struct channel_program *cp, union scsw *scsw)
> >   	u32 cpa = scsw->cmd.cpa;
> >   	u32 ccw_head, ccw_tail;
> >   
> > +	if (!cp->initialized)
> > +		return;
> > +
> >   	/*
> >   	 * LATER:
> >   	 * For now, only update the cmd.cpa part. We may need to deal with
> > diff --git a/drivers/s390/cio/vfio_ccw_cp.h b/drivers/s390/cio/vfio_ccw_cp.h
> > index a4b74fb1aa57..3c20cd208da5 100644
> > --- a/drivers/s390/cio/vfio_ccw_cp.h
> > +++ b/drivers/s390/cio/vfio_ccw_cp.h
> > @@ -21,6 +21,7 @@
> >    * @ccwchain_list: list head of ccwchains
> >    * @orb: orb for the currently processed ssch request
> >    * @mdev: the mediated device to perform page pinning/unpinning
> > + * @initialized: whether this instance is actually initialized
> >    *
> >    * @ccwchain_list is the head of a ccwchain list, that contents the
> >    * translated result of the guest channel program that pointed out by
> > @@ -30,6 +31,7 @@ struct channel_program {
> >   	struct list_head ccwchain_list;
> >   	union orb orb;
> >   	struct device *mdev;
> > +	bool initialized;
> >   };
> >   
> >   extern int cp_init(struct channel_program *cp, struct device *mdev,
> > diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
> > index 890c588a3a61..83d6f43792b6 100644
> > --- a/drivers/s390/cio/vfio_ccw_drv.c
> > +++ b/drivers/s390/cio/vfio_ccw_drv.c
> > @@ -79,8 +79,7 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
> >   	private = container_of(work, struct vfio_ccw_private, io_work);
> >   	irb = &private->irb;
> >   
> > -	if (scsw_is_solicited(&irb->scsw) &&
> > -	    (scsw_fctl(&irb->scsw) & SCSW_FCTL_START_FUNC)) {
> > +	if (scsw_is_solicited(&irb->scsw)) {
> >   		cp_update_scsw(&private->cp, &irb->scsw);
> >   		cp_free(&private->cp);
> >   	}
> >   
> 
> The changes look good to me.

Thanks!

> 
> Thanks
> Farhan
>