Re: [PATCH v4 13/15] KVM: s390: configure the guest's AP devices

Pierre Morel
2018-04-16T13:05:58Z

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.

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.

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?

> + 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.

> + 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)

--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany