From: Pierre Morel <pmorel@linux.vnet.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: pasic@linux.vnet.ibm.com, bjsdjshi@linux.vnet.ibm.com,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [PATCH 10/10] vfio: ccw: Let user wait when busy on IO
Date: Wed, 25 Apr 2018 16:00:05 +0200 [thread overview]
Message-ID: <d20bbfac-f97b-c1f5-3b1d-3bf66502e93b@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180425104841.758a314d.cohuck@redhat.com>
On 25/04/2018 10:48, Cornelia Huck wrote:
> On Thu, 19 Apr 2018 16:48:13 +0200
> Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:
>
>> In the current implementation, we do not want to start a new SSCH
>> command before the last one ends.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
>> ---
>> drivers/s390/cio/vfio_ccw_fsm.c | 3 +++
>> drivers/s390/cio/vfio_ccw_ops.c | 21 ++++++++++++++++++++-
>> drivers/s390/cio/vfio_ccw_private.h | 4 +++-
>> 3 files changed, 26 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
>> index b77b8ad..4140292 100644
>> --- a/drivers/s390/cio/vfio_ccw_fsm.c
>> +++ b/drivers/s390/cio/vfio_ccw_fsm.c
>> @@ -195,6 +195,9 @@ static int fsm_irq(struct vfio_ccw_private *private)
>> if (private->io_trigger)
>> eventfd_signal(private->io_trigger, 1);
>>
>> + if (private->io_completion)
>> + complete(private->io_completion);
>> +
>> return VFIO_CCW_STATE_IDLE;
>> }
>>
>> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
>> index f0f4071..346532d 100644
>> --- a/drivers/s390/cio/vfio_ccw_ops.c
>> +++ b/drivers/s390/cio/vfio_ccw_ops.c
>> @@ -171,6 +171,8 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
>> struct vfio_ccw_private *private;
>> struct ccw_io_region *region;
>> union scsw *scsw;
>> + int max_retries = 5;
>> + DECLARE_COMPLETION_ONSTACK(completion);
>>
>> if (*ppos + count > sizeof(*region))
>> return -EINVAL;
>> @@ -185,7 +187,24 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
>> if ((scsw->cmd.fctl & SCSW_FCTL_START_FUNC) != SCSW_FCTL_START_FUNC)
>> return -EINVAL;
>>
>> - vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_SSCH_REQ);
>> + do {
>> + switch (private->state) {
>> + case VFIO_CCW_STATE_BUSY:
>> + private->io_completion = &completion;
>> + wait_for_completion(&completion);
>> + break;
>> + case VFIO_CCW_STATE_IDLE:
>> + if (!vfio_ccw_fsm_event(private,
>> + VFIO_CCW_EVENT_SSCH_REQ))
>> + return count;
>> + break;
>> + default:
>> + return -EBUSY;
>> + }
>> + } while (max_retries--);
> I really don't think we want to go there. If we are busy, generate an
> indication to that respect, but don't retry. My preferred approach
> would be to keep the "we're busy" times as small as possible and let
> the host channel subsystem handle any further races. We can't make that
> bulletproof anyway, so no reason to make life more difficult for us.
OK, clear.
Thanks
Pierre
>
>> +
>> + if (max_retries <= 0)
>> + return -EBUSY;
>> if (region->ret_code != 0)
>> return region->ret_code;
>>
>> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
>> index dbef727..7cca078 100644
>> --- a/drivers/s390/cio/vfio_ccw_private.h
>> +++ b/drivers/s390/cio/vfio_ccw_private.h
>> @@ -39,6 +39,7 @@ struct vfio_ccw_private {
>> struct subchannel *sch;
>> int state;
>> struct completion *completion;
>> + struct completion *io_completion;
>> atomic_t avail;
>> struct mdev_device *mdev;
>> struct notifier_block nb;
>> @@ -93,12 +94,13 @@ enum vfio_ccw_event {
>> typedef int (fsm_func_t)(struct vfio_ccw_private *);
>> extern fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS];
>>
>> -static inline void vfio_ccw_fsm_event(struct vfio_ccw_private *private,
>> +static inline int vfio_ccw_fsm_event(struct vfio_ccw_private *private,
>> int event)
>> {
>> mutex_lock(&private->state_mutex);
>> private->state = vfio_ccw_jumptable[private->state][event](private);
>> mutex_unlock(&private->state_mutex);
>> + return private->io_region.ret_code;
>> }
>>
>> extern struct workqueue_struct *vfio_ccw_work_q;
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
prev parent reply other threads:[~2018-04-25 14:00 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-19 14:48 [PATCH 00/10] vfio: ccw: Refactoring the VFIO CCW state machine Pierre Morel
2018-04-19 14:48 ` [PATCH 01/10] vfio: ccw: Moving state change out of IRQ context Pierre Morel
[not found] ` <20180424065442.GV12194@bjsdjshi@linux.vnet.ibm.com>
2018-04-24 8:40 ` Pierre Morel
2018-04-24 9:59 ` Cornelia Huck
2018-04-24 11:49 ` Pierre Morel
2018-04-24 11:55 ` Cornelia Huck
2018-04-24 13:07 ` Pierre Morel
2018-04-24 16:42 ` Halil Pasic
2018-04-25 6:57 ` Cornelia Huck
2018-04-25 11:06 ` Halil Pasic
2018-04-30 13:56 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 02/10] vfio: ccw: Transform FSM functions to return state Pierre Morel
[not found] ` <20180424072550.GW12194@bjsdjshi@linux.vnet.ibm.com>
2018-04-24 8:22 ` Pierre Morel
2018-04-30 13:58 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 03/10] vfio: ccw: new SCH_EVENT event Pierre Morel
2018-04-25 8:25 ` Cornelia Huck
2018-04-25 13:54 ` Pierre Morel
[not found] ` <20180426065954.GP5428@bjsdjshi@linux.vnet.ibm.com>
2018-04-30 15:28 ` Cornelia Huck
2018-05-04 8:25 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ event Pierre Morel
2018-04-25 8:41 ` Cornelia Huck
[not found] ` <24f638e4-2f7e-00e1-1efb-ff3fe524bca0@linux.vnet.ibm.com>
2018-04-30 15:30 ` Cornelia Huck
2018-05-03 12:06 ` Pierre Morel
2018-05-22 15:38 ` Cornelia Huck
2018-05-23 8:19 ` Pierre Morel
[not found] ` <20180426073053.GZ12194@bjsdjshi@linux.vnet.ibm.com>
[not found] ` <20180426074806.GB12194@bjsdjshi@linux.vnet.ibm.com>
2018-04-30 15:33 ` Cornelia Huck
[not found] ` <20180502074622.GV5428@bjsdjshi@linux.vnet.ibm.com>
2018-05-02 8:22 ` Cornelia Huck
2018-05-03 14:26 ` Pierre Morel
[not found] ` <20180504011916.GA26081@bjsdjshi@linux.ibm.com>
2018-05-04 11:02 ` Pierre Morel
2018-05-22 15:41 ` Cornelia Huck
2018-05-23 7:50 ` Pierre Morel
2018-05-23 8:10 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 05/10] vfio: ccw: Suppress unused event parameter Pierre Morel
[not found] ` <20180426073618.GA12194@bjsdjshi@linux.vnet.ibm.com>
2018-05-03 10:34 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 06/10] vfio: ccw: Make FSM functions atomic Pierre Morel
2018-04-19 14:48 ` [PATCH 07/10] vfio: ccw: Introduce the INIT event Pierre Morel
2018-04-30 15:39 ` Cornelia Huck
2018-05-03 10:31 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 08/10] vfio: ccw: Handling reset and shutdown with states Pierre Morel
2018-04-30 15:43 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 09/10] vfio: ccw: Suppressing the BOXED state Pierre Morel
2018-04-25 8:44 ` Cornelia Huck
2018-04-25 13:55 ` Pierre Morel
2018-04-30 15:47 ` Cornelia Huck
2018-05-03 9:02 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 10/10] vfio: ccw: Let user wait when busy on IO Pierre Morel
2018-04-25 8:48 ` Cornelia Huck
2018-04-25 14:00 ` Pierre Morel [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d20bbfac-f97b-c1f5-3b1d-3bf66502e93b@linux.vnet.ibm.com \
--to=pmorel@linux.vnet.ibm.com \
--cc=bjsdjshi@linux.vnet.ibm.com \
--cc=cohuck@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=pasic@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).