linux-kernel - Re: [PATCH v4 1/1] s390/vfio-ap: fix circular lockdep when setting/clearing crypto masks

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Message-ID: <20210318001729.06cdb8d6.pasic@linux.ibm.com>
Date:   Thu, 18 Mar 2021 00:17:29 +0100
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, stable@...r.kernel.org,
        borntraeger@...ibm.com, cohuck@...hat.com, kwankhede@...dia.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pasic@...ux.vnet.ibm.com
Subject: Re: [PATCH v4 1/1] s390/vfio-ap: fix circular lockdep when
 setting/clearing crypto masks

On Wed, 10 Mar 2021 10:05:59 -0500
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> -		ret = vfio_ap_mdev_reset_queues(mdev);
> +		matrix_mdev = mdev_get_drvdata(mdev);

Is it guaranteed that matrix_mdev can't be NULL here? If yes, please
remind me of the mechanism that ensures this.

> +
> +		/*
> +		 * 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 == false,
> +			       mutex_unlock(&matrix_dev->lock),
> +			       mutex_lock(&matrix_dev->lock));
> +
> +		if (matrix_mdev->kvm)
> +			ret = vfio_ap_mdev_reset_queues(mdev);
> +		else
> +			ret = -ENODEV;

Didn't we agree to make the call to vfio_ap_mdev_reset_queues()
unconditional again (for reference please take look at 
Message-ID: <64afa72c-2d6a-2ca1-e576-34e15fa579ed@...ux.ibm.com>)?

Regards,
Halil