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

[Tony Krowiak]

On 08/15/2018 05:52 AM, Cornelia Huck wrote:
> On Mon, 13 Aug 2018 17:48:07 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> 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.

Right you are! Will change it.

> > +	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.

It is, but I think it describes exactly what the function does.

> > +	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?

You are correct, if the APID is not assigned, then the corresponding bit 
will be
cleared regardless. In a previous version, the functions failed if the 
APID is
not assigned, but a colleague removed that check. I guess it makes sense 
given
it really does not hurt anything to ask to unassign an APID that isn't 
assigned
to begin with. Would you prefer I update the comment, or do you feel the 
user
should be made aware of an attempt to unassign an APID that is not assigned?

> > + *
> > + * 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.

That is good news indeed.

>