linux-kernel - Re: [PATCH v11 07/14] s390/vfio-ap: sysfs attribute to display the guest's matrix

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Message-ID: <20201028091758.73aa77a3.pasic@linux.ibm.com>
Date:   Wed, 28 Oct 2020 09:17:58 +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, freude@...ux.ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, mjrosato@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v11 07/14] s390/vfio-ap: sysfs attribute to display the
 guest's matrix

On Thu, 22 Oct 2020 13:12:02 -0400
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> +static ssize_t guest_matrix_show(struct device *dev,
> +				 struct device_attribute *attr, char *buf)
> +{
> +	ssize_t nchars;
> +	struct mdev_device *mdev = mdev_from_dev(dev);
> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +
> +	if (!vfio_ap_mdev_has_crycb(matrix_mdev))
> +		return -ENODEV;

I'm wondering, would it make sense to have guest_matrix display the would
be guest matrix when we don't have a KVM? With the filtering in
place, the question in what guest_matrix would my (assign) matrix result
right now if I were to hook up my vfio_ap_mdev to a guest seems a
legitimate one.


> +
> +	mutex_lock(&matrix_dev->lock);
> +	nchars = vfio_ap_mdev_matrix_show(&matrix_mdev->shadow_apcb, buf);
> +	mutex_unlock(&matrix_dev->lock);
> +
> +	return nchars;
> +}
> +static DEVICE_ATTR_RO(guest_matrix);