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,
borntraeger@de.ibm.com, cohuck@redhat.com,
pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com, jgg@nvidia.com,
alex.williamson@redhat.com, kwankhede@nvidia.com,
david@redhat.com
Subject: Re: [PATCH 2/2] s390/vfio-ap: replace open coded locks for VFIO_GROUP_NOTIFY_SET_KVM notification
Date: Wed, 21 Jul 2021 16:45:50 +0200 [thread overview]
Message-ID: <20210721164550.5402fe1c.pasic@linux.ibm.com> (raw)
In-Reply-To: <20210719193503.793910-3-akrowiak@linux.ibm.com>
On Mon, 19 Jul 2021 15:35:03 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:
> It was pointed out during an unrelated patch review that locks should not
[..]
> -static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
> +static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev,
> + struct kvm *kvm)
> {
> - /*
> - * If the KVM pointer is in the process of being set, wait until the
> - * process has completed.
> - */
> - wait_event_cmd(matrix_mdev->wait_for_kvm,
> - !matrix_mdev->kvm_busy,
> - mutex_unlock(&matrix_dev->lock),
> - mutex_lock(&matrix_dev->lock));
> -
> - if (matrix_mdev->kvm) {
We used to check if matrix_mdev->kvm is null, but ...
> - matrix_mdev->kvm_busy = true;
> - mutex_unlock(&matrix_dev->lock);
> -
> - if (matrix_mdev->kvm->arch.crypto.crycbd) {
> - down_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem);
> - matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
> - up_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem);
> -
> - kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
> - }
> + if (kvm->arch.crypto.crycbd) {
... now we just try to dereference it. And ..
> + down_write(&kvm->arch.crypto.pqap_hook_rwsem);
> + kvm->arch.crypto.pqap_hook = NULL;
> + up_write(&kvm->arch.crypto.pqap_hook_rwsem);
>
> + mutex_lock(&kvm->lock);
> mutex_lock(&matrix_dev->lock);
> +
> + kvm_arch_crypto_clear_masks(kvm);
> vfio_ap_mdev_reset_queues(matrix_mdev->mdev);
> - kvm_put_kvm(matrix_mdev->kvm);
> + kvm_put_kvm(kvm);
> matrix_mdev->kvm = NULL;
> - matrix_mdev->kvm_busy = false;
> - wake_up_all(&matrix_mdev->wait_for_kvm);
> +
> + mutex_unlock(&kvm->lock);
> + mutex_unlock(&matrix_dev->lock);
> }
> }
>
[..]
> @@ -1363,14 +1323,11 @@ 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);
> - vfio_ap_mdev_unset_kvm(matrix_mdev);
> - mutex_unlock(&matrix_dev->lock);
> -
.. before access to the matrix_mdev->kvm used to be protected by
the matrix_dev->lock ...
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> &matrix_mdev->iommu_notifier);
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> &matrix_mdev->group_notifier);
> + vfio_ap_mdev_unset_kvm(matrix_mdev, matrix_mdev->kvm);
... but it is not any more. BTW I don't think the code is guaranteed
to fetch ->kvm just once.
Can you please explain why can we get away with being more
lax when dealing with matrix_mdev->kvm?
Regards,
Halil
[..]
next prev parent reply other threads:[~2021-07-21 14:46 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 19:35 [PATCH 0/2] s390/vfio-ap: do not open code locks for VFIO_GROUP_NOTIFY_SET_KVM notification Tony Krowiak
2021-07-19 19:35 ` [PATCH 1/2] s390/vfio-ap: r/w lock for PQAP interception handler function pointer Tony Krowiak
2021-08-18 17:03 ` Christian Borntraeger
2021-08-18 23:25 ` Halil Pasic
2021-08-19 6:56 ` Christian Borntraeger
2021-08-19 13:36 ` Tony Krowiak
2021-08-19 21:42 ` Halil Pasic
2021-08-23 13:08 ` Tony Krowiak
2021-08-19 13:20 ` Tony Krowiak
2021-08-19 17:54 ` Alex Williamson
2021-08-19 17:58 ` Jason Gunthorpe
2021-08-20 15:59 ` Tony Krowiak
2021-08-20 22:05 ` Tony Krowiak
2021-08-20 22:30 ` Jason Gunthorpe
2021-08-23 15:17 ` Tony Krowiak
2021-08-20 22:41 ` Alex Williamson
2021-08-23 20:51 ` Tony Krowiak
2021-07-19 19:35 ` [PATCH 2/2] s390/vfio-ap: replace open coded locks for VFIO_GROUP_NOTIFY_SET_KVM notification Tony Krowiak
2021-07-21 14:45 ` Halil Pasic [this message]
2021-07-22 13:09 ` Tony Krowiak
2021-07-23 14:26 ` Halil Pasic
2021-07-23 21:24 ` Tony Krowiak
2021-07-26 20:36 ` Halil Pasic
2021-07-26 22:03 ` Jason Gunthorpe
2021-07-26 22:43 ` Halil Pasic
2021-07-28 13:43 ` Tony Krowiak
2021-07-28 19:42 ` Halil Pasic
2021-07-30 13:33 ` Tony Krowiak
2021-07-27 6:54 ` Christoph Hellwig
2021-07-21 19:37 ` Jason J. Herne
2021-07-22 13:16 ` Tony Krowiak
2021-08-02 13:10 ` [PATCH 0/2] s390/vfio-ap: do not open code " Tony Krowiak
2021-08-02 13:53 ` Halil Pasic
2021-08-02 16:32 ` Tony Krowiak
2021-08-03 13:08 ` Jason Gunthorpe
2021-08-03 13:34 ` Tony Krowiak
2021-08-18 15:59 ` Christian Borntraeger
2021-08-18 16:39 ` Alex Williamson
2021-08-18 16:50 ` Christian Borntraeger
2021-08-18 22:52 ` Halil Pasic
2021-08-19 15:30 ` Cornelia Huck
2021-08-20 14:24 ` Tony Krowiak
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