From: Tony Krowiak <akrowiak@linux.ibm.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com,
alex.williamson@redhat.com, kwankhede@nvidia.com,
david@redhat.com
Subject: Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated
Date: Fri, 4 Dec 2020 11:48:24 -0500 [thread overview]
Message-ID: <a5a613ef-4c74-ad68-46bd-7159fbafef47@linux.ibm.com> (raw)
In-Reply-To: <20201203185514.54060568.pasic@linux.ibm.com>
On 12/3/20 12:55 PM, Halil Pasic wrote:
> On Wed, 2 Dec 2020 18:41:01 -0500
> Tony Krowiak <akrowiak@linux.ibm.com> wrote:
>
>> The vfio_ap device driver registers a group notifier with VFIO when the
>> file descriptor for a VFIO mediated device for a KVM guest is opened to
>> receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM
>> event). When the KVM pointer is set, the vfio_ap driver stashes the pointer
>> and calls the kvm_get_kvm() function to increment its reference counter.
>> When the notifier is called to make notification that the KVM pointer has
>> been set to NULL, the driver should clean up any resources associated with
>> the KVM pointer and decrement its reference counter. The current
>> implementation does not take care of this clean up.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Do we need a Fixes tag? Do we need this backported? In my opinion
> this is necessary since the interrupt patches.
I'll put in a fixes tag:
Fixes: 258287c994de (s390: vfio-ap: implement mediated device open callback)
Yes, this should probably be backported.
>
>> ---
>> drivers/s390/crypto/vfio_ap_ops.c | 21 +++++++++++++--------
>> 1 file changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> index e0bde8518745..eeb9c9130756 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -1083,6 +1083,17 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
>> return NOTIFY_DONE;
>> }
>>
>> +static void vfio_ap_mdev_put_kvm(struct ap_matrix_mdev *matrix_mdev)
> I don't like the name. The function does more that put_kvm. Maybe
> something like _disconnect_kvm()?
Since the vfio_ap_mdev_set_kvm() function is called by the
notifier when the KVM pointer is set, how about:
vfio_ap_mdev_unset_kvm()
for when the KVM pointer is nullified?
>
>> +{
>> + if (matrix_mdev->kvm) {
>> + (matrix_mdev->kvm);
>> + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
> Is a plain assignment to arch.crypto.pqap_hook apropriate, or do we need
> to take more care?
>
> For instance kvm_arch_crypto_set_masks() takes kvm->lock before poking
> kvm->arch.crypto.crycb.
>
>> + vfio_ap_mdev_reset_queues(matrix_mdev->mdev);
>> + kvm_put_kvm(matrix_mdev->kvm);
>> + matrix_mdev->kvm = NULL;
>> + }
>> +}
>> +
>> static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>> unsigned long action, void *data)
>> {
>> @@ -1095,7 +1106,7 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>> matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier);
>>
>> if (!data) {
>> - matrix_mdev->kvm = NULL;
>> + vfio_ap_mdev_put_kvm(matrix_mdev);
> The lock question was already raised.
>
> What are the exact circumstances under which this branch can be taken?
>
>> return NOTIFY_OK;
>> }
>>
>> @@ -1222,13 +1233,7 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
>> struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>>
>> mutex_lock(&matrix_dev->lock);
>> - if (matrix_mdev->kvm) {
>> - kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
>> - matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
>> - vfio_ap_mdev_reset_queues(mdev);
>> - kvm_put_kvm(matrix_mdev->kvm);
>> - matrix_mdev->kvm = NULL;
>> - }
>> + vfio_ap_mdev_put_kvm(matrix_mdev);
>> mutex_unlock(&matrix_dev->lock);
>>
>> vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
next prev parent reply other threads:[~2020-12-04 16:49 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 23:41 [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated Tony Krowiak
2020-12-03 10:19 ` Cornelia Huck
2020-12-03 17:01 ` Halil Pasic
2020-12-03 19:14 ` Tony Krowiak
2020-12-03 17:55 ` Halil Pasic
2020-12-04 14:43 ` Tony Krowiak
2020-12-04 19:05 ` Halil Pasic
2020-12-04 19:46 ` Tony Krowiak
2020-12-04 21:54 ` Halil Pasic
2020-12-07 18:50 ` Tony Krowiak
2020-12-08 0:01 ` Halil Pasic
[not found] ` <e196b743-74d8-398b-4b3e-4a64002d9bfc@linux.ibm.com>
2020-12-13 22:57 ` Halil Pasic
2020-12-04 16:48 ` Tony Krowiak [this message]
2020-12-04 16:57 ` Cornelia Huck
2020-12-04 19:47 ` Tony Krowiak
2020-12-07 15:24 ` Halil Pasic
2020-12-07 15:42 ` Christian Borntraeger
2020-12-07 19:05 ` Tony Krowiak
2020-12-08 0:40 ` Halil Pasic
2020-12-11 21:08 ` Tony Krowiak
2020-12-13 23:13 ` Halil Pasic
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