linux-kernel - Re: [PATCH v9 10/22] s390: vfio-ap: sysfs interfaces to configure adapters

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Date:   Wed, 15 Aug 2018 11:52:42 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com, Tony Krowiak <akrowiak@...ux.ibm.com>
Subject: Re: [PATCH v9 10/22] s390: vfio-ap: sysfs interfaces to configure
 adapters

On Mon, 13 Aug 2018 17:48:07 -0400
Tony Krowiak <akrowiak@...ux.vnet.ibm.com> wrote:

> +/**
> + * assign_adapter_store
> + *
> + * @dev: the matrix device
> + * @attr: a mediated matrix device attribute
> + * @buf: a buffer containing the adapter ID (APID) to be assigned
> + * @count: the number of bytes in @buf
> + *
> + * Parses the APID from @buf and assigns it to the mediated matrix device.
> + *
> + * Returns the number of bytes processed if the APID is valid; otherwise returns
> + * an error.
> + */
> +static ssize_t assign_adapter_store(struct device *dev,
> +				    struct device_attribute *attr,
> +				    const char *buf, size_t count)
> +{
> +	int ret = 0;

You don't need to initialize this to 0, as kstrtoul will set it in any
case.

> +	unsigned long apid;
> +	struct mdev_device *mdev = mdev_from_dev(dev);
> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +	unsigned long max_apid = matrix_mdev->matrix.apm_max;
> +
> +	ret = kstrtoul(buf, 0, &apid);
> +	if (ret)
> +		return ret;
> +	if (apid > max_apid)
> +		return -EINVAL;
> +
> +	/* Set the bit in the AP mask (APM) corresponding to the AP adapter
> +	 * number (APID). The bits in the mask, from most significant to least
> +	 * significant bit, correspond to APIDs 0-255.
> +	 */
> +	mutex_lock(&matrix_dev.lock);
> +
> +	ret = vfio_ap_mdev_verify_queues_reserved_for_apid(matrix_mdev, apid);

That function name really is a mouthful :) I don't have any better
suggestions, though.

> +	if (ret)
> +		goto done;
> +
> +	set_bit_inv(apid, matrix_mdev->matrix.apm);
> +
> +	ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev);
> +	if (ret)
> +		goto share_err;
> +
> +	ret = count;
> +	goto done;
> +
> +share_err:
> +	clear_bit_inv(apid, matrix_mdev->matrix.apm);
> +done:
> +	mutex_unlock(&matrix_dev.lock);
> +
> +	return ret;
> +}
> +static DEVICE_ATTR_WO(assign_adapter);
> +
> +/**
> + * unassign_adapter_store
> + *
> + * @dev: the matrix device
> + * @attr: a mediated matrix device attribute
> + * @buf: a buffer containing the adapter ID (APID) to be assigned
> + * @count: the number of bytes in @buf
> + *
> + * Parses the APID from @buf and unassigns it from the mediated matrix device.
> + * The APID must be a valid value

A valid value, but not necessarily assigned, right?

> + *
> + * Returns the number of bytes processed if the APID is valid; otherwise returns
> + * an error.
> + */
> +static ssize_t unassign_adapter_store(struct device *dev,
> +				      struct device_attribute *attr,
> +				      const char *buf, size_t count)
> +{
> +	int ret;
> +	unsigned long apid;
> +	struct mdev_device *mdev = mdev_from_dev(dev);
> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +
> +	ret = kstrtoul(buf, 0, &apid);
> +	if (ret)
> +		return ret;
> +
> +	if (apid > matrix_mdev->matrix.apm_max)
> +		return -EINVAL;
> +
> +	mutex_lock(&matrix_dev.lock);
> +	clear_bit_inv((unsigned long)apid, matrix_mdev->matrix.apm);
> +	mutex_unlock(&matrix_dev.lock);
> +
> +	return count;
> +}
> +DEVICE_ATTR_WO(unassign_adapter);

In general, looks good to me.