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    Subject[PATCH v6 14/21] s390: vfio-ap: implement mediated device open callback
    Date
    Implements the open callback on the mediated matrix device.
    The function registers a group notifier to receive notification
    of the VFIO_GROUP_NOTIFY_SET_KVM event. When notified,
    the vfio_ap device driver will get access to the guest's
    kvm structure. The open callback must ensure that only one
    mediated device shall be opened per guest.

    Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
    ---
    drivers/s390/crypto/vfio_ap_ops.c | 128 +++++++++++++++++++++++++++++++++
    drivers/s390/crypto/vfio_ap_private.h | 2 +
    2 files changed, 130 insertions(+), 0 deletions(-)

    diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
    index bc7398d..58be495 100644
    --- a/drivers/s390/crypto/vfio_ap_ops.c
    +++ b/drivers/s390/crypto/vfio_ap_ops.c
    @@ -11,6 +11,10 @@
    #include <linux/device.h>
    #include <linux/list.h>
    #include <linux/ctype.h>
    +#include <linux/bitops.h>
    +#include <linux/kvm_host.h>
    +#include <linux/module.h>
    +#include <asm/kvm.h>

    #include "vfio_ap_private.h"

    @@ -748,12 +752,136 @@ static ssize_t matrix_show(struct device *dev, struct device_attribute *attr,
    NULL
    };

    +/**
    + * Verify that the AP instructions are available on the guest and are to be
    + * interpreted by the firmware. The former is indicated via the
    + * KVM_S390_VM_CPU_FEAT_AP CPU model feature and the latter by apie crypto
    + * flag.
    + */
    +static int kvm_ap_validate_crypto_setup(struct kvm *kvm)
    +{
    + if (test_bit_inv(KVM_S390_VM_CPU_FEAT_AP, kvm->arch.cpu_feat) &&
    + kvm->arch.crypto.apie)
    + return 0;
    +
    + pr_err("%s: interpretation of AP instructions not available",
    + VFIO_AP_MODULE_NAME);
    +
    + return -EOPNOTSUPP;
    +}
    +
    +static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
    + unsigned long action, void *data)
    +{
    + struct ap_matrix_mdev *matrix_mdev;
    +
    + if (action == VFIO_GROUP_NOTIFY_SET_KVM) {
    + matrix_mdev = container_of(nb, struct ap_matrix_mdev,
    + group_notifier);
    + matrix_mdev->kvm = data;
    + }
    +
    + return NOTIFY_OK;
    +}
    +
    +/**
    + * vfio_ap_mdev_open_once
    + *
    + * @matrix_mdev: a mediated matrix device
    + *
    + * Return 0 if no other mediated matrix device has been opened for the
    + * KVM guest assigned to @matrix_mdev; otherwise, returns an error.
    + */
    +static int vfio_ap_mdev_open_once(struct ap_matrix_mdev *matrix_mdev)
    +{
    + int ret = 0;
    + struct ap_matrix_mdev *lstdev;
    +
    + spin_lock_bh(&mdev_list_lock);
    +
    + list_for_each_entry(lstdev, &mdev_list, list) {
    + if ((lstdev->kvm == matrix_mdev->kvm) &&
    + (lstdev != matrix_mdev)) {
    + ret = -EPERM;
    + break;
    + }
    + }
    +
    + if (ret) {
    + pr_err("%s: mdev %s open failed for guest %s",
    + VFIO_AP_MODULE_NAME, matrix_mdev->name,
    + matrix_mdev->kvm->arch.dbf->name);
    + pr_err("%s: mdev %s already opened for guest %s",
    + VFIO_AP_MODULE_NAME, lstdev->name,
    + lstdev->kvm->arch.dbf->name);
    + }
    +
    + spin_unlock_bh(&mdev_list_lock);
    + return ret;
    +}
    +
    +static int vfio_ap_mdev_open(struct mdev_device *mdev)
    +{
    + struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    + struct ap_matrix_dev *matrix_dev =
    + to_ap_matrix_dev(mdev_parent_dev(mdev));
    + unsigned long events;
    + int ret;
    +
    + if (!try_module_get(THIS_MODULE))
    + return -ENODEV;
    +
    + ret = vfio_ap_verify_queues_reserved(matrix_dev, matrix_mdev->name,
    + &matrix_mdev->matrix);
    + if (ret)
    + goto out_err;
    +
    + matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier;
    + events = VFIO_GROUP_NOTIFY_SET_KVM;
    +
    + ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    + &events, &matrix_mdev->group_notifier);
    + if (ret)
    + goto out_err;
    +
    + ret = kvm_ap_validate_crypto_setup(matrix_mdev->kvm);
    + if (ret)
    + goto out_kvm_err;
    +
    + ret = vfio_ap_mdev_open_once(matrix_mdev);
    + if (ret)
    + goto out_kvm_err;
    +
    + return 0;
    +
    +out_kvm_err:
    + vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    + &matrix_mdev->group_notifier);
    + matrix_mdev->kvm = NULL;
    +out_err:
    + module_put(THIS_MODULE);
    +
    + return ret;
    +}
    +
    +static void vfio_ap_mdev_release(struct mdev_device *mdev)
    +{
    + struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    +
    + vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    + &matrix_mdev->group_notifier);
    + matrix_mdev->kvm = NULL;
    + module_put(THIS_MODULE);
    +}
    +
    static const struct mdev_parent_ops vfio_ap_matrix_ops = {
    .owner = THIS_MODULE,
    .supported_type_groups = vfio_ap_mdev_type_groups,
    .mdev_attr_groups = vfio_ap_mdev_attr_groups,
    .create = vfio_ap_mdev_create,
    .remove = vfio_ap_mdev_remove,
    + .open = vfio_ap_mdev_open,
    + .release = vfio_ap_mdev_release,
    };

    int vfio_ap_mdev_register(struct ap_matrix_dev *matrix_dev)
    diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
    index ae771f5..7792b45 100644
    --- a/drivers/s390/crypto/vfio_ap_private.h
    +++ b/drivers/s390/crypto/vfio_ap_private.h
    @@ -56,6 +56,8 @@ struct ap_matrix_mdev {
    const char *name;
    struct list_head list;
    struct ap_matrix matrix;
    + struct notifier_block group_notifier;
    + struct kvm *kvm;
    };

    static struct ap_matrix_dev *to_ap_matrix_dev(struct device *dev)
    --
    1.7.1
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