linux-kernel - Re: [PATCH v2] s390/vfio-ap: fix sysfs status attribute for AP queue devices

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Message-ID: <17ef8d76-5dec-46a3-84e1-1b92fadd27b0@linux.ibm.com>
Date:   Wed, 8 Nov 2023 15:21:20 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     jjherne@...ux.ibm.com, pasic@...ux.ibm.com,
        borntraeger@...ux.ibm.com, frankja@...ux.ibm.com,
        imbrenda@...ux.ibm.com, david@...hat.com,
        Harald Freudenberger <freude@...ux.ibm.com>
Subject: Re: [PATCH v2] s390/vfio-ap: fix sysfs status attribute for AP queue
 devices

Christian,
Can this be pushed with the Acks by Halil and Harald?

On 11/8/23 15:11, Tony Krowiak wrote:
> The 'status' attribute for AP queue devices bound to the vfio_ap device
> driver displays incorrect status when the mediated device is attached to a
> guest, but the queue device is not passed through. In the current
> implementation, the status displayed is 'in_use' which is not correct; it
> should be 'assigned'. This can happen if one of the queue devices
> associated with a given adapter is not bound to the vfio_ap device driver.
> For example:
> 
> Queues listed in /sys/bus/ap/drivers/vfio_ap:
> 14.0005
> 14.0006
> 14.000d
> 16.0006
> 16.000d
> 
> Queues listed in /sys/devices/vfio_ap/matrix/$UUID/matrix
> 14.0005
> 14.0006
> 14.000d
> 16.0005
> 16.0006
> 16.000d
> 
> Queues listed in /sys/devices/vfio_ap/matrix/$UUID/guest_matrix
> 14.0005
> 14.0006
> 14.000d
> 
> The reason no queues for adapter 0x16 are listed in the guest_matrix is
> because queue 16.0005 is not bound to the vfio_ap device driver, so no
> queue associated with the adapter is passed through to the guest;
> therefore, each queue device for adapter 0x16 should display 'assigned'
> instead of 'in_use', because those queues are not in use by a guest, but
> only assigned to the mediated device.
> 
> Let's check the AP configuration for the guest to determine whether a
> queue device is passed through before displaying a status of 'in_use'.
> 
> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
> Acked-by: Halil Pasic <pasic@...ux.ibm.com>
> Acked-by: Harald Freudenberger <freude@...ux.ibm.com>
> ---
>   drivers/s390/crypto/vfio_ap_ops.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 4db538a55192..6e0a79086656 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -1976,6 +1976,7 @@ static ssize_t status_show(struct device *dev,
>   {
>   	ssize_t nchars = 0;
>   	struct vfio_ap_queue *q;
> +	unsigned long apid, apqi;
>   	struct ap_matrix_mdev *matrix_mdev;
>   	struct ap_device *apdev = to_ap_dev(dev);
>   
> @@ -1983,8 +1984,21 @@ static ssize_t status_show(struct device *dev,
>   	q = dev_get_drvdata(&apdev->device);
>   	matrix_mdev = vfio_ap_mdev_for_queue(q);
>   
> +	/* If the queue is assigned to the matrix mediated device, then
> +	 * determine whether it is passed through to a guest; otherwise,
> +	 * indicate that it is unassigned.
> +	 */
>   	if (matrix_mdev) {
> -		if (matrix_mdev->kvm)
> +		apid = AP_QID_CARD(q->apqn);
> +		apqi = AP_QID_QUEUE(q->apqn);
> +		/*
> +		 * If the queue is passed through to the guest, then indicate
> +		 * that it is in use; otherwise, indicate that it is
> +		 * merely assigned to a matrix mediated device.
> +		 */
> +		if (matrix_mdev->kvm &&
> +		    test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
> +		    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
>   			nchars = scnprintf(buf, PAGE_SIZE, "%s\n",
>   					   AP_QUEUE_IN_USE);
>   		else