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Thu, 16 Jun 2022 17:14:18 +0000 (GMT) Message-ID: Subject: Re: [PATCH v2 07/10] vfio/ccw: Create an OPEN FSM Event From: Eric Farman To: Matthew Rosato Cc: Jason Gunthorpe , Alex Williamson , Cornelia Huck , Halil Pasic , kvm@vger.kernel.org, linux-s390@vger.kernel.org Date: Thu, 16 Jun 2022 13:14:16 -0400 In-Reply-To: <0816ab3a-8601-0462-6c2b-4ba7fa8a1e2b@linux.ibm.com> References: <20220615203318.3830778-1-farman@linux.ibm.com> <20220615203318.3830778-8-farman@linux.ibm.com> <0816ab3a-8601-0462-6c2b-4ba7fa8a1e2b@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: AXPt8elTIl48zxQBP97gfypFDfx3ac6W X-Proofpoint-GUID: pCRxnDe65lRL0HXIPVfgpFY00NzW2bLs X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.64.514 definitions=2022-06-16_14,2022-06-16_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=923 suspectscore=0 bulkscore=0 clxscore=1015 adultscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 mlxscore=0 spamscore=0 lowpriorityscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2206160071 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Thu, 2022-06-16 at 12:33 -0400, Matthew Rosato wrote: > On 6/15/22 4:33 PM, Eric Farman wrote: > > Move the process of enabling a subchannel for use by vfio-ccw > > into the FSM, such that it can manage the sequence of lifecycle > > events for the device. > > > > That is, if the FSM state is NOT_OPER(erational), then do the work > > that would enable the subchannel and move the FSM to STANDBY state. > > An attempt to perform this event again from any of the other > > operating > > states (IDLE, CP_PROCESSING, CP_PENDING) will convert the device > > back > > to NOT_OPER so the configuration process can be started again. > > Except STANDBY, which ignores the event via fsm_nop. I wonder > though, > whether that's the right thing to do. For each of the other states > you're saying 'if it's already open, go back to NOT_OPER so we can > start > over' -- In this case a STANDBY->STANDBY is also a case of 'it's > already > open' so shouldn't we also go back to NOT_OPER so we can start over? Yeah, the subchannel's already been probed but the mdev hasn't yet. (Or perhaps it did, but that failed.) I was viewing it as a "well there's nothing to do here" but you're right that the rest of the entries take a "oh that's unexpected, go to NOT_OPER" approach. So should make that consistent here, since it would be quite a surprise. > > Seems to me really we just don't expect to ever get an OPEN event > unless > we are in NOT_OPER. > > If there's a reason to keep STANDBY->STANDBY as a nop, but we don't > expect to see it and don't' want to WARN because of it, then maybe a > log > entry at least would make sense. > > As for the IDLE/CP_PROCESSING/CP_PENDING cases, going fsm_notoper > because this is unexpected probably makes sense, but the logging is > going to be really confusing (before this change, you know that you > called fsm_notoper because you got VFIO_CCW_EVENT_NOT_OPER -- now > you'll > see a log entry cut for NOT_OPER but won't be sure if it was for > EVENT_NOT_OPER or EVENT_OPEN). Maybe you can look at 'event' inside > fsm_notoper and cut a slightly different trace entry when arriving > here > for EVENT_OPEN? Yeah, good idea. Since we don't expect any of these in normal behavior, perhaps I'll trace both state and event, instead of trying to make conditionals out of everything. > > ... > > > +static void fsm_open(struct vfio_ccw_private *private, > > + enum vfio_ccw_event event) > > +{ > > + struct subchannel *sch = private->sch; > > + int ret; > > + > > + spin_lock_irq(sch->lock); > > + sch->isc = VFIO_CCW_ISC; > > + ret = cio_enable_subchannel(sch, (u32)(unsigned long)sch); > > + if (!ret) > > + private->state = VFIO_CCW_STATE_STANDBY; > > nit: could get rid of 'ret' and just do > > if (!cio_enable...) > private->state = VFIO_CCW_STATE_STANDBY; Ah, fair. Cut/paste and didn't really consider the simplification. I see that I left the unconditional "private->state = STANDBY" in the hunk just above this, which can be removed. (I finally do in patch 10.) Will make that change too. > > > + spin_unlock_irq(sch->lock); > > +} > > + > > /* > > * Device statemachine > > */ > > @@ -373,29 +389,34 @@ fsm_func_t > > *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = { > > [VFIO_CCW_EVENT_IO_REQ] = fsm_io_error, > > [VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_error, > > [VFIO_CCW_EVENT_INTERRUPT] = fsm_disabled_irq, > > + [VFIO_CCW_EVENT_OPEN] = fsm_open, > > }, > > [VFIO_CCW_STATE_STANDBY] = { > > [VFIO_CCW_EVENT_NOT_OPER] = fsm_notoper, > > [VFIO_CCW_EVENT_IO_REQ] = fsm_io_error, > > [VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_error, > > [VFIO_CCW_EVENT_INTERRUPT] = fsm_irq, > > + [VFIO_CCW_EVENT_OPEN] = fsm_nop, > > }, > > [VFIO_CCW_STATE_IDLE] = { > > [VFIO_CCW_EVENT_NOT_OPER] = fsm_notoper, > > [VFIO_CCW_EVENT_IO_REQ] = fsm_io_request, > > [VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_request, > > [VFIO_CCW_EVENT_INTERRUPT] = fsm_irq, > > + [VFIO_CCW_EVENT_OPEN] = fsm_notoper, > > }, > > [VFIO_CCW_STATE_CP_PROCESSING] = { > > [VFIO_CCW_EVENT_NOT_OPER] = fsm_notoper, > > [VFIO_CCW_EVENT_IO_REQ] = fsm_io_retry, > > [VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_retry, > > [VFIO_CCW_EVENT_INTERRUPT] = fsm_irq, > > + [VFIO_CCW_EVENT_OPEN] = fsm_notoper, > > }, > > [VFIO_CCW_STATE_CP_PENDING] = { > > [VFIO_CCW_EVENT_NOT_OPER] = fsm_notoper, > > [VFIO_CCW_EVENT_IO_REQ] = fsm_io_busy, > > [VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_request, > > [VFIO_CCW_EVENT_INTERRUPT] = fsm_irq, > > + [VFIO_CCW_EVENT_OPEN] = fsm_notoper, > > }, > > }; > > diff --git a/drivers/s390/cio/vfio_ccw_private.h > > b/drivers/s390/cio/vfio_ccw_private.h > > index 4cfdd5fc0961..8dff1699a7d9 100644 > > --- a/drivers/s390/cio/vfio_ccw_private.h > > +++ b/drivers/s390/cio/vfio_ccw_private.h > > @@ -142,6 +142,7 @@ enum vfio_ccw_event { > > VFIO_CCW_EVENT_IO_REQ, > > VFIO_CCW_EVENT_INTERRUPT, > > VFIO_CCW_EVENT_ASYNC_REQ, > > + VFIO_CCW_EVENT_OPEN, > > /* last element! */ > > NR_VFIO_CCW_EVENTS > > };