From mboxrd@z Thu Jan 1 00:00:00 1970 From: Farhan Ali Subject: Re: [PATCH 3/3] vfio-ccw: add handling for asnyc channel instructions Date: Wed, 28 Nov 2018 10:55:11 -0500 Message-ID: References: <20181122165432.4437-1-cohuck@redhat.com> <20181122165432.4437-4-cohuck@redhat.com> <20181128100249.72d4299a.cohuck@redhat.com> <25021742-a7a8-a90c-a2a3-eb8a78bf1fb0@linux.ibm.com> <20181128155201.5be1d582.cohuck@redhat.com> <1feb66c0-ce80-2853-1522-e7d787471fd3@linux.ibm.com> <20181128163547.7eb33873.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-s390@vger.kernel.org, Eric Farman , Alex Williamson , Pierre Morel , kvm@vger.kernel.org, qemu-devel@nongnu.org, Halil Pasic , qemu-s390x@nongnu.org To: Cornelia Huck Return-path: In-Reply-To: <20181128163547.7eb33873.cohuck@redhat.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On 11/28/2018 10:35 AM, Cornelia Huck wrote: > On Wed, 28 Nov 2018 10:00:59 -0500 > Farhan Ali wrote: > >> On 11/28/2018 09:52 AM, Cornelia Huck wrote: >>> On Wed, 28 Nov 2018 09:31:51 -0500 >>> Farhan Ali wrote: >>> >>>> On 11/28/2018 04:02 AM, Cornelia Huck wrote: >>>>> On Tue, 27 Nov 2018 14:09:49 -0500 >>>>> Farhan Ali wrote: >>>>> >>>>>> On 11/22/2018 11:54 AM, Cornelia Huck wrote: >>>>>>> Add a region to the vfio-ccw device that can be used to submit >>>>>>> asynchronous I/O instructions. ssch continues to be handled by the >>>>>>> existing I/O region; the new region handles hsch and csch. >>>>>>> >>>>>>> Interrupt status continues to be reported through the same channels >>>>>>> as for ssch. >>>>>>> >>>>>>> Signed-off-by: Cornelia Huck >>>>>>> --- >>>>>>> drivers/s390/cio/Makefile | 3 +- >>>>>>> drivers/s390/cio/vfio_ccw_async.c | 88 ++++++++++++++++ >>>>>>> drivers/s390/cio/vfio_ccw_drv.c | 48 ++++++--- >>>>>>> drivers/s390/cio/vfio_ccw_fsm.c | 158 +++++++++++++++++++++++++++- >>>>>>> drivers/s390/cio/vfio_ccw_ops.c | 13 ++- >>>>>>> drivers/s390/cio/vfio_ccw_private.h | 6 ++ >>>>>>> include/uapi/linux/vfio.h | 4 + >>>>>>> include/uapi/linux/vfio_ccw.h | 12 +++ >>>>>>> 8 files changed, 313 insertions(+), 19 deletions(-) >>>>>>> create mode 100644 drivers/s390/cio/vfio_ccw_async.c >>>>>>> >>>>> >>>>>>> @@ -76,7 +79,8 @@ 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)) { >>>>>>> + if (scsw_is_solicited(&irb->scsw) && >>>>>>> + (scsw_fctl(&irb->scsw) & SCSW_FCTL_START_FUNC)) { >>>>>>> cp_update_scsw(&private->cp, &irb->scsw); >>>>>>> cp_free(&private->cp); >>>>>>> } >>>>>> >>>>>> I am a little confused about this. Why do we need to update the scsw.cpa >>>>>> if we have the start function function control bit set? Is it an >>>>>> optimization? >>>>> >>>>> No, it's not an optimization. This is the work function that is >>>>> scheduled if we get an interrupt for the device. Previously, we only >>>>> got an interrupt if either the device presented us an unsolicited >>>>> status or if we got an interrupt as a response to the channel program >>>>> we submitted. Now, we can get an interrupt for halt/clear subchannel as >>>>> well, and in that case, we don't necessarily have a cp. >>>>> >>>>> [Thinking some more about it, we need to verify if the start function >>>>> actually remains set if we try to terminate a running channel program >>>>> with halt/clear. A clear might scrub too much. If that's the case, we >>>>> also need to free the cp if the start function is not set.] >>>>> >>>>> >>>> >>>> According to PoPs (Chapter 16: I/O interruptions, under function control): >>>> >>>> The start-function indication is also cleared at >>>> the subchannel during the execution of CLEAR SUB- >>>> CHANNEL. >>>> >>>> So maybe we do need to free the cp. >>> >>> Hm... so we need to make sure that cp_update_scsw() and cp_free() only >>> do something when there's actually a valid cp around and call them >>> unconditionally. >> >> Yes, I agree. >> >>> Maybe add a ->valid flag to struct channel_program? >> >> We could do that. So we would set the flag once we have copied the >> channel program to kernel memory? since that's when we should care about >> freeing it. > > I hacked up the following (still untested): > > From e771c8dc5abbfbd19688b452096bab9d032e0df5 Mon Sep 17 00:00:00 2001 > From: Cornelia Huck > 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 > --- > 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(-) > > 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 Farhan