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    SubjectRe: [PATCH v10 09/16] s390/vfio-ap: allow assignment of unavailable AP queues to mdev device
    On Fri, 21 Aug 2020 15:56:09 -0400
    Tony Krowiak <akrowiak@linux.ibm.com> wrote:

    > The current implementation does not allow assignment of an AP adapter or
    > domain to an mdev device if the APQNs resulting from the assignment
    > do not reference AP queue devices that are bound to the vfio_ap device
    > driver. This patch allows assignment of AP resources to the matrix mdev as
    > long as the APQNs resulting from the assignment:
    > 1. Are not reserved by the AP BUS for use by the zcrypt device drivers.
    > 2. Are not assigned to another matrix mdev.
    >
    > The rationale behind this is twofold:
    > 1. The AP architecture does not preclude assignment of APQNs to an AP
    > configuration that are not available to the system.
    > 2. APQNs that do not reference a queue device bound to the vfio_ap
    > device driver will not be assigned to the guest's CRYCB, so the
    > guest will not get access to queues not bound to the vfio_ap driver.
    >
    > Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
    > ---
    > drivers/s390/crypto/vfio_ap_ops.c | 212 +++++-------------------------
    > 1 file changed, 35 insertions(+), 177 deletions(-)
    >
    > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
    > index eaf4e9eab6cb..24fd47e43b80 100644
    > --- a/drivers/s390/crypto/vfio_ap_ops.c
    > +++ b/drivers/s390/crypto/vfio_ap_ops.c
    > @@ -1,4 +1,3 @@
    > -// SPDX-License-Identifier: GPL-2.0+

    Probably not intentional, or?

    > /*
    > * Adjunct processor matrix VFIO device driver callbacks.
    > *
    > @@ -420,122 +419,6 @@ static struct attribute_group *vfio_ap_mdev_type_groups[] = {
    > NULL,
    > };
    >
    > -struct vfio_ap_queue_reserved {
    > - unsigned long *apid;
    > - unsigned long *apqi;
    > - bool reserved;
    > -};
    > -
    > -/**
    > - * vfio_ap_has_queue
    > - *
    > - * @dev: an AP queue device
    > - * @data: a struct vfio_ap_queue_reserved reference
    > - *
    > - * Flags whether the AP queue device (@dev) has a queue ID containing the APQN,
    > - * apid or apqi specified in @data:
    > - *
    > - * - If @data contains both an apid and apqi value, then @data will be flagged
    > - * as reserved if the APID and APQI fields for the AP queue device matches
    > - *
    > - * - If @data contains only an apid value, @data will be flagged as
    > - * reserved if the APID field in the AP queue device matches
    > - *
    > - * - If @data contains only an apqi value, @data will be flagged as
    > - * reserved if the APQI field in the AP queue device matches
    > - *
    > - * Returns 0 to indicate the input to function succeeded. Returns -EINVAL if
    > - * @data does not contain either an apid or apqi.
    > - */
    > -static int vfio_ap_has_queue(struct device *dev, void *data)
    > -{
    > - struct vfio_ap_queue_reserved *qres = data;
    > - struct ap_queue *ap_queue = to_ap_queue(dev);
    > - ap_qid_t qid;
    > - unsigned long id;
    > -
    > - if (qres->apid && qres->apqi) {
    > - qid = AP_MKQID(*qres->apid, *qres->apqi);
    > - if (qid == ap_queue->qid)
    > - qres->reserved = true;
    > - } else if (qres->apid && !qres->apqi) {
    > - id = AP_QID_CARD(ap_queue->qid);
    > - if (id == *qres->apid)
    > - qres->reserved = true;
    > - } else if (!qres->apid && qres->apqi) {
    > - id = AP_QID_QUEUE(ap_queue->qid);
    > - if (id == *qres->apqi)
    > - qres->reserved = true;
    > - } else {
    > - return -EINVAL;
    > - }
    > -
    > - return 0;
    > -}
    > -
    > -/**
    > - * vfio_ap_verify_queue_reserved
    > - *
    > - * @matrix_dev: a mediated matrix device
    > - * @apid: an AP adapter ID
    > - * @apqi: an AP queue index
    > - *
    > - * Verifies that the AP queue with @apid/@apqi is reserved by the VFIO AP device
    > - * driver according to the following rules:
    > - *
    > - * - If both @apid and @apqi are not NULL, then there must be an AP queue
    > - * device bound to the vfio_ap driver with the APQN identified by @apid and
    > - * @apqi
    > - *
    > - * - If only @apid is not NULL, then there must be an AP queue device bound
    > - * to the vfio_ap driver with an APQN containing @apid
    > - *
    > - * - If only @apqi is not NULL, then there must be an AP queue device bound
    > - * to the vfio_ap driver with an APQN containing @apqi
    > - *
    > - * Returns 0 if the AP queue is reserved; otherwise, returns -EADDRNOTAVAIL.
    > - */
    > -static int vfio_ap_verify_queue_reserved(unsigned long *apid,
    > - unsigned long *apqi)
    > -{
    > - int ret;
    > - struct vfio_ap_queue_reserved qres;
    > -
    > - qres.apid = apid;
    > - qres.apqi = apqi;
    > - qres.reserved = false;
    > -
    > - ret = driver_for_each_device(&matrix_dev->vfio_ap_drv->driver, NULL,
    > - &qres, vfio_ap_has_queue);
    > - if (ret)
    > - return ret;
    > -
    > - if (qres.reserved)
    > - return 0;
    > -
    > - return -EADDRNOTAVAIL;
    > -}
    > -
    > -static int
    > -vfio_ap_mdev_verify_queues_reserved_for_apid(struct ap_matrix_mdev *matrix_mdev,
    > - unsigned long apid)
    > -{
    > - int ret;
    > - unsigned long apqi;
    > - unsigned long nbits = matrix_mdev->matrix.aqm_max + 1;
    > -
    > - if (find_first_bit_inv(matrix_mdev->matrix.aqm, nbits) >= nbits)
    > - return vfio_ap_verify_queue_reserved(&apid, NULL);
    > -
    > - for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, nbits) {
    > - ret = vfio_ap_verify_queue_reserved(&apid, &apqi);
    > - if (ret)
    > - return ret;
    > - }
    > -
    > - return 0;
    > -}
    > -
    > #define MDEV_SHARING_ERR "Userspace may not re-assign queue %02lx.%04lx " \
    > "already assigned to %s"
    >
    > @@ -572,6 +455,11 @@ static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev,
    > DECLARE_BITMAP(aqm, AP_DOMAINS);
    >
    > list_for_each_entry(lstdev, &matrix_dev->mdev_list, node) {
    > + /*
    > + * If either of the input masks belongs to the mdev to which an
    > + * AP resource is being assigned, then we don't need to verify
    > + * that mdev's masks.
    > + */
    > if (matrix_mdev == lstdev)
    > continue;
    >

    Seems unrelated.

    > @@ -597,6 +485,20 @@ static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev,
    > return 0;
    > }
    >
    > +static int vfio_ap_mdev_validate_masks(struct ap_matrix_mdev *matrix_mdev,
    > + unsigned long *mdev_apm,
    > + unsigned long *mdev_aqm)
    > +{
    > + DECLARE_BITMAP(apm, AP_DEVICES);
    > + DECLARE_BITMAP(aqm, AP_DOMAINS);
    > +
    > + if (bitmap_and(apm, mdev_apm, ap_perms.apm, AP_DEVICES) &&
    > + bitmap_and(aqm, mdev_aqm, ap_perms.aqm, AP_DOMAINS))

    Isn't ap_perms supposed to be protected by ap_perms_mutex? In theory
    you could end up with a torn write (catch the a[pq]mask_commit() with
    its pants down, in a sense that only a part of the memcpy was done (and
    became observable on the other CPU doing this validate).

    > + return -EADDRNOTAVAIL;
    > +
    > + return vfio_ap_mdev_verify_no_sharing(matrix_mdev, mdev_apm, mdev_aqm);
    > +}
    > +
    > /**
    > * vfio_ap_mdev_filter_matrix
    > *
    > @@ -882,33 +784,21 @@ static ssize_t assign_adapter_store(struct device *dev,
    > if (apid > matrix_mdev->matrix.apm_max)
    > return -ENODEV;
    >
    > - /*
    > - * 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);
    > - if (ret)
    > - goto done;
    > -
    > memset(apm, 0, sizeof(apm));
    > set_bit_inv(apid, apm);
    >
    > - ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev, apm,
    > - matrix_mdev->matrix.aqm);
    > - if (ret)
    > - goto done;
    > -
    > + mutex_lock(&matrix_dev->lock);
    > + ret = vfio_ap_mdev_validate_masks(matrix_mdev, apm,
    > + matrix_mdev->matrix.aqm);
    > + if (ret) {
    > + mutex_unlock(&matrix_dev->lock);
    > + return ret;
    > + }

    At this point the ap_perms may have already changed, or?

    > set_bit_inv(apid, matrix_mdev->matrix.apm);
    > vfio_ap_mdev_link_queues(matrix_mdev, LINK_APID, apid);
    > - ret = count;
    > -
    > -done:
    > mutex_unlock(&matrix_dev->lock);
    >
    > - return ret;
    > + return count;
    > }
    > static DEVICE_ATTR_WO(assign_adapter);
    >
    > @@ -958,26 +848,6 @@ static ssize_t unassign_adapter_store(struct device *dev,
    > }
    > static DEVICE_ATTR_WO(unassign_adapter);
    >
    > -static int
    > -vfio_ap_mdev_verify_queues_reserved_for_apqi(struct ap_matrix_mdev *matrix_mdev,
    > - unsigned long apqi)
    > -{
    > - int ret;
    > - unsigned long apid;
    > - unsigned long nbits = matrix_mdev->matrix.apm_max + 1;
    > -
    > - if (find_first_bit_inv(matrix_mdev->matrix.apm, nbits) >= nbits)
    > - return vfio_ap_verify_queue_reserved(NULL, &apqi);
    > -
    > - for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, nbits) {
    > - ret = vfio_ap_verify_queue_reserved(&apid, &apqi);
    > - if (ret)
    > - return ret;
    > - }
    > -
    > - return 0;
    > -}
    > -
    > /**
    > * assign_domain_store
    > *
    > @@ -1031,28 +901,21 @@ static ssize_t assign_domain_store(struct device *dev,
    > if (apqi > max_apqi)
    > return -ENODEV;
    >
    > - mutex_lock(&matrix_dev->lock);
    > -
    > - ret = vfio_ap_mdev_verify_queues_reserved_for_apqi(matrix_mdev, apqi);
    > - if (ret)
    > - goto done;
    > -
    > memset(aqm, 0, sizeof(aqm));
    > set_bit_inv(apqi, aqm);
    >
    > - ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev,
    > - matrix_mdev->matrix.apm, aqm);
    > - if (ret)
    > - goto done;
    > -
    > + mutex_lock(&matrix_dev->lock);
    > + ret = vfio_ap_mdev_validate_masks(matrix_mdev, matrix_mdev->matrix.apm,
    > + aqm);
    > + if (ret) {
    > + mutex_unlock(&matrix_dev->lock);
    > + return ret;
    > + }
    > set_bit_inv(apqi, matrix_mdev->matrix.aqm);
    > vfio_ap_mdev_link_queues(matrix_mdev, LINK_APQI, apqi);
    > - ret = count;
    > -
    > -done:
    > mutex_unlock(&matrix_dev->lock);
    >
    > - return ret;
    > + return count;
    > }
    > static DEVICE_ATTR_WO(assign_domain);
    >
    > @@ -1139,11 +1002,6 @@ static ssize_t assign_control_domain_store(struct device *dev,
    > if (id > matrix_mdev->matrix.adm_max)
    > return -ENODEV;
    >
    > - /* Set the bit in the ADM (bitmask) corresponding to the AP control
    > - * domain number (id). The bits in the mask, from most significant to
    > - * least significant, correspond to IDs 0 up to the one less than the
    > - * number of control domains that can be assigned.
    > - */
    > mutex_lock(&matrix_dev->lock);
    > set_bit_inv(id, matrix_mdev->matrix.adm);
    > mutex_unlock(&matrix_dev->lock);

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