From: Halil Pasic <pasic@linux.ibm.com>
To: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, freude@linux.ibm.com,
borntraeger@de.ibm.com, cohuck@redhat.com,
mjrosato@linux.ibm.com, alex.williamson@redhat.com,
kwankhede@nvidia.com, fiuczy@linux.ibm.com,
frankja@linux.ibm.com, david@redhat.com, hca@linux.ibm.com,
gor@linux.ibm.com
Subject: Re: [PATCH v11 01/14] s390/vfio-ap: No need to disable IRQ after queue reset
Date: Fri, 30 Oct 2020 18:42:42 +0100 [thread overview]
Message-ID: <20201030184242.3bceee09.pasic@linux.ibm.com> (raw)
In-Reply-To: <7a2c5930-9c37-8763-7e5d-c08a3638e6a1@linux.ibm.com>
On Thu, 29 Oct 2020 19:29:35 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:
> >> @@ -1177,7 +1166,10 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
> >> */
> >> if (ret)
> >> rc = ret;
> >> - vfio_ap_irq_disable_apqn(AP_MKQID(apid, apqi));
> >> + q = vfio_ap_get_queue(matrix_mdev,
> >> + AP_MKQID(apid, apqi));
> >> + if (q)
> >> + vfio_ap_free_aqic_resources(q);
> > Is it safe to do vfio_ap_free_aqic_resources() at this point? I don't
> > think so. I mean does the current code (and vfio_ap_mdev_reset_queue()
> > in particular guarantee that the reset is actually done when we arrive
> > here)? BTW, I think we have a similar problem with the current code as
> > well.
>
> If the return code from the vfio_ap_mdev_reset_queue() function
> is zero, then yes, we are guaranteed the reset was done and the
> queue is empty.
I've read up on this and I disagree. We should discuss this offline.
> The function returns a non-zero return code if
> the reset fails or the queue the reset did not complete within a given
> amount of time, so maybe we shouldn't free AQIC resources when
> we get a non-zero return code from the reset function?
>
If the queue is gone, or broken, it won't produce interrupts or poke the
notifier bit, and we should clean up the AQIC resources.
> There are three occasions when the vfio_ap_mdev_reset_queues()
> is called:
> 1. When the VFIO_DEVICE_RESET ioctl is invoked from userspace
> (i.e., when the guest is started)
> 2. When the mdev fd is closed (vfio_ap_mdev_release())
> 3. When the mdev is removed (vfio_ap_mdev_remove())
>
> The IRQ resources are initialized when the PQAP(AQIC)
> is intercepted to enable interrupts. This would occur after
> the guest boots and the AP bus initializes. So, 1 would
> presumably occur before that happens. I couldn't find
> anywhere in the AP bus or zcrypt code where a PQAP(AQIC)
> is executed to disable interrupts, so my assumption is
> that IRQ disablement is accomplished by a reset on
> the guest. I'll have to ask Harald about that. So, 2 would
> occur when the guest is about to terminate and 3
> would occur only after the guest is terminated. In any
> case, it seems that IRQ resources should be cleaned up.
> Maybe it would be more appropriate to do that in the
> vfio_ap_mdev_release() and vfio_ap_mdev_remove()
> functions themselves?
I'm a bit confused. But I think you are wrong. What happens when the
guest reIPLs? I guess the subsystem reset should also do the
VFIO_DEVICE_RESET ioctl, and that has to reset the queues and disable
the interrupts. Or?
Regards,
Halil
next prev parent reply other threads:[~2020-10-30 17:42 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-22 17:11 [PATCH v11 00/14] s390/vfio-ap: dynamic configuration support Tony Krowiak
2020-10-22 17:11 ` [PATCH v11 01/14] s390/vfio-ap: No need to disable IRQ after queue reset Tony Krowiak
2020-10-22 19:44 ` kernel test robot
2020-10-26 16:57 ` Tony Krowiak
2020-10-27 6:48 ` Halil Pasic
2020-10-29 23:29 ` Tony Krowiak
2020-10-30 16:13 ` Tony Krowiak
2020-10-30 17:27 ` Halil Pasic
2020-10-30 20:45 ` Tony Krowiak
2020-10-30 17:42 ` Halil Pasic [this message]
2020-10-30 20:37 ` Tony Krowiak
2020-10-31 3:43 ` Halil Pasic
2020-11-02 14:35 ` Tony Krowiak
2020-10-30 17:54 ` Halil Pasic
2020-10-30 20:53 ` Tony Krowiak
2020-10-30 21:13 ` Tony Krowiak
2020-10-30 17:56 ` Halil Pasic
2020-10-30 21:17 ` Tony Krowiak
2020-10-22 17:11 ` [PATCH v11 02/14] 390/vfio-ap: use new AP bus interface to search for queue devices Tony Krowiak
2020-10-27 7:01 ` Halil Pasic
2020-11-02 21:57 ` Tony Krowiak
2020-10-22 17:11 ` [PATCH v11 03/14] s390/vfio-ap: manage link between queue struct and matrix mdev Tony Krowiak
2020-10-27 9:33 ` Halil Pasic
2020-10-22 17:11 ` [PATCH v11 04/14] s390/zcrypt: driver callback to indicate resource in use Tony Krowiak
2020-10-27 13:01 ` Halil Pasic
2020-10-27 16:55 ` Harald Freudenberger
2020-11-13 21:30 ` Tony Krowiak
2020-11-14 0:00 ` Halil Pasic
2020-11-16 16:23 ` Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 05/14] s390/vfio-ap: implement in-use callback for vfio_ap driver Tony Krowiak
2020-10-27 13:27 ` Halil Pasic
2020-11-13 17:14 ` Tony Krowiak
2020-11-13 23:47 ` Halil Pasic
2020-11-16 16:58 ` Tony Krowiak
2020-11-23 17:03 ` Cornelia Huck
2020-11-23 19:23 ` Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 06/14] s390/vfio-ap: introduce shadow APCB Tony Krowiak
2020-10-28 8:11 ` Halil Pasic
2020-11-13 17:18 ` Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 07/14] s390/vfio-ap: sysfs attribute to display the guest's matrix Tony Krowiak
2020-10-28 8:17 ` Halil Pasic
2020-11-13 17:27 ` Tony Krowiak
2020-11-13 23:12 ` Halil Pasic
2020-11-19 18:15 ` Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 08/14] s390/vfio-ap: hot plug/unplug queues on bind/unbind of queue device Tony Krowiak
2020-10-22 20:30 ` kernel test robot
2020-10-26 17:04 ` Tony Krowiak
2020-10-28 13:57 ` Halil Pasic
2020-11-03 22:49 ` Tony Krowiak
2020-11-04 12:52 ` Halil Pasic
2020-11-04 21:20 ` Tony Krowiak
2020-11-05 12:27 ` Halil Pasic
2020-11-13 20:36 ` Tony Krowiak
2020-11-04 13:23 ` Halil Pasic
2020-10-22 17:12 ` [PATCH v11 09/14] s390/vfio-ap: allow assignment of unavailable AP queues to mdev device Tony Krowiak
2020-10-28 15:03 ` Halil Pasic
2020-10-22 17:12 ` [PATCH v11 10/14] s390/vfio-ap: allow hot plug/unplug of AP resources using " Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 11/14] s390/zcrypt: Notify driver on config changed and scan complete callbacks Tony Krowiak
2020-10-27 17:28 ` Harald Freudenberger
2020-11-13 20:58 ` Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 12/14] s390/vfio-ap: handle host AP config change notification Tony Krowiak
2020-10-22 21:17 ` kernel test robot
2020-10-26 17:07 ` Tony Krowiak
2020-10-26 17:21 ` Tony Krowiak
2020-11-03 9:48 ` kernel test robot
2020-11-13 21:06 ` Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 13/14] s390/vfio-ap: handle AP bus scan completed notification Tony Krowiak
2020-10-22 17:12 ` [PATCH v11 14/14] s390/vfio-ap: update docs to include dynamic config support Tony Krowiak
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