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    SubjectRe: [PATCH v4 13/15] KVM: s390: configure the guest's AP devices
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    On 04/16/2018 09:05 AM, Pierre Morel wrote:
    > On 15/04/2018 23:22, Tony Krowiak wrote:
    >> Registers a group notifier during the open of the mediated
    >> matrix device to get information on KVM presence through the
    >> VFIO_GROUP_NOTIFY_SET_KVM event. When notified, the pointer
    >> to the kvm structure is saved inside the mediated matrix
    >> device. Once the VFIO AP device driver has access to KVM,
    >> access to the APs can be configured for the guest.
    >>
    >> Access to APs is configured when the file descriptor for the
    >> mediated matrix device is opened by userspace. The items to be
    >> configured are:
    >>
    >> 1. The ECA.28 bit in the SIE state description determines whether
    >> AP instructions are interpreted by the hardware or intercepted.
    >> The VFIO AP device driver relies interpretive execution of
    >> AP instructions so the ECA.28 bit will be set
    >>
    >> 2. Guest access to AP adapters, usage domains and control domains
    >> is controlled by three bit masks referenced from the
    >> Crypto Control Block (CRYCB) referenced from the guest's SIE state
    >> description:
    >>
    >> * The AP Mask (APM) controls access to the AP adapters. Each bit
    >> in the APM represents an adapter number - from most significant
    >> to least significant bit - from 0 to 255. The bits in the APM
    >> are set according to the adapter numbers assigned to the mediated
    >> matrix device via its 'assign_adapter' sysfs attribute file.
    >>
    >> * The AP Queue (AQM) controls access to the AP queues. Each bit
    >> in the AQM represents an AP queue index - from most significant
    >> to least significant bit - from 0 to 255. A queue index references
    >> a specific domain and is synonymous with the domian number. The
    >> bits in the AQM are set according to the domain numbers assigned
    >> to the mediated matrix device via its 'assign_domain' sysfs
    >> attribute file.
    >>
    >> * The AP Domain Mask (ADM) controls access to the AP control
    >> domains.
    >> Each bit in the ADM represents a control domain - from most
    >> significant to least significant bit - from 0-255. The
    >> bits in the ADM are set according to the domain numbers assigned
    >> to the mediated matrix device via its 'assign_control_domain'
    >> sysfs attribute file.
    >>
    >> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
    >> ---
    >> drivers/s390/crypto/vfio_ap_ops.c | 50
    >> +++++++++++++++++++++++++++++++++
    >> drivers/s390/crypto/vfio_ap_private.h | 2 +
    >> 2 files changed, 52 insertions(+), 0 deletions(-)
    >>
    >> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
    >> b/drivers/s390/crypto/vfio_ap_ops.c
    >> index bc2b05e..e3ff5ab 100644
    >> --- a/drivers/s390/crypto/vfio_ap_ops.c
    >> +++ b/drivers/s390/crypto/vfio_ap_ops.c
    >> @@ -53,6 +53,54 @@ static int vfio_ap_mdev_remove(struct mdev_device
    >> *mdev)
    >> return 0;
    >> }
    >>
    >> +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;
    >> +}
    >> +
    >> +static int vfio_ap_mdev_open(struct mdev_device *mdev)
    >> +{
    >> + struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    >> + unsigned long events;
    >> + int ret;
    >> +
    >> + 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)
    >> + return ret;
    >> +
    >> + ret = kvm_ap_interpret_instructions(matrix_mdev->kvm, true);
    >
    > Do you need this call ?
    > apie is always enabled in KVM if AP instructions are available.

    I suppose we don't, in which case we don't need the
    kvm_ap_interpret_instructions()
    function either ... at least not until we implement interception.

    >
    >
    > Setting or not the interpretation is done for the VM in a all.
    > It is not the right place to do it here since open is device dependent.

    As I stated above, at this time we probably do not need this, however;
    that will not always be the case. The setting is and always will be for the
    VM in all - unless the architecture changes - because it is controlled by a
    single bit (ECA.28). If you recall, I originally set interpretation in the
    vfio_ap device driver when notified of the VFIO_GROUP_NOTIFY_SET_KVM event.
    I believe ultimately that it is the device driver that should set the value
    for apie.



    >
    >
    > Or we only have one device in the VM at a time.
    > In this case, shouldn't we make it official by returning -EEXIST for
    > the second call?

    We do allow only one vfio-ap device at a time. QEMU will allow only one
    vfio-ap device
    to be configured for a guest. Should we also put a check in here?

    >
    >
    >
    >> + if (ret)
    >> + return ret;
    >> +
    >> + ret = kvm_ap_configure_matrix(matrix_mdev->kvm,
    >> + matrix_mdev->matrix);
    >> +
    >> + return ret;
    >> +}
    >> +
    >> +static void vfio_ap_mdev_release(struct mdev_device *mdev)
    >> +{
    >> + struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    >> +
    >> + kvm_ap_deconfigure_matrix(matrix_mdev->kvm);
    >> + kvm_ap_interpret_instructions(matrix_mdev->kvm, false);
    >
    > This call clears the apie in KVM.
    > This is only OK if we have a single device present until the end of
    > the VM,
    > otherwise AP instructions in the guest will fail after the release
    > until the end of the VM
    > or until a new device is plugged.

    See Message ID:
    <1523819244-29954-5-git-send-email-akrowiak@linux.vnet.ibm.com> on the
    qemu mailing list. There will be only one vfio-ap device allowed for the
    MVP model.

    >
    >
    >
    >> + vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    >> + &matrix_mdev->group_notifier);
    >> +}
    >> +
    >> static ssize_t name_show(struct kobject *kobj, struct device *dev,
    >> char *buf)
    >> {
    >> return sprintf(buf, "%s\n", VFIO_AP_MDEV_NAME_HWVIRT);
    >> @@ -754,6 +802,8 @@ static ssize_t matrix_show(struct device *dev,
    >> struct device_attribute *attr,
    >> .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 *ap_matrix)
    >> diff --git a/drivers/s390/crypto/vfio_ap_private.h
    >> b/drivers/s390/crypto/vfio_ap_private.h
    >> index f248faf..48e2806 100644
    >> --- a/drivers/s390/crypto/vfio_ap_private.h
    >> +++ b/drivers/s390/crypto/vfio_ap_private.h
    >> @@ -31,6 +31,8 @@ struct ap_matrix {
    >>
    >> struct ap_matrix_mdev {
    >> struct kvm_ap_matrix *matrix;
    >> + struct notifier_block group_notifier;
    >> + struct kvm *kvm;
    >> };
    >>
    >> static inline struct ap_matrix *to_ap_matrix(struct device *dev)
    >
    >

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