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, stable@vger.kernel.org,
borntraeger@de.ibm.com, cohuck@redhat.com, kwankhede@nvidia.com,
pbonzini@redhat.com, alex.williamson@redhat.com,
pasic@linux.vnet.ibm.com
Subject: Re: [PATCH v3 1/1] s390/vfio-ap: fix circular lockdep when setting/clearing crypto masks
Date: Wed, 3 Mar 2021 20:42:11 +0100 [thread overview]
Message-ID: <20210303204211.4c021c25.pasic@linux.ibm.com> (raw)
In-Reply-To: <e5cc2a81-7273-2b3e-0d4c-c6c17502bdae@linux.ibm.com>
On Wed, 3 Mar 2021 11:41:22 -0500
Tony Krowiak <akrowiak@linux.ibm.com> wrote:
> > How do you exect userspace to react to this -ENODEV?
>
> The VFIO_DEVICE_RESET ioctl expects a return code.
> The vfio_ap_mdev_reset_queues() function can return -EIO or
> -EBUSY, so I would expect userspace to handle -ENODEV
> similarly to -EIO or any other non-zero return code. I also
> looked at all of the VFIO_DEVICE_RESET calls from QEMU to see
> how the return from the ioctl call is handled:
>
> * ap: reports the reset failed along with the rc
And carries on as if nothing happened. There is not much smart
userspace can do in such a situation. Therefore the reset really
should not fail.
Please note that in this particular case, if the userspace would
opt for a retry, we would most likely end up in a retry loop.
> * ccw: doesn't check the rc
> * pci: kind of hard to follow without digging deep, but definitely
> handles non-zero rc.
>
> I think the caller should be notified whether the queues were
> successfully reset or not, and why; in this case, the answer is
> there are no devices to reset.
That is the wrong answer. The ioctl is supposed to reset the
ap_matrix_mdev device. The ap_matrix_mdev device still exists. Thus
returning -ENODEV is bugous.
Regards,
Halil
next prev parent reply other threads:[~2021-03-03 22:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-02 20:43 [PATCH v3 0/1] s390/vfio-ap: fix circular lockdep when starting SE guest Tony Krowiak
2021-03-02 20:43 ` [PATCH v3 1/1] s390/vfio-ap: fix circular lockdep when setting/clearing crypto masks Tony Krowiak
2021-03-03 15:23 ` Halil Pasic
2021-03-03 16:41 ` Tony Krowiak
2021-03-03 19:42 ` Halil Pasic [this message]
2021-03-04 16:22 ` Tony Krowiak
2021-03-03 17:10 ` Tony Krowiak
2021-03-03 19:47 ` Halil Pasic
2021-03-04 17:43 ` Tony Krowiak
2021-03-09 10:23 ` Halil Pasic
2021-03-09 14:27 ` Tony Krowiak
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