Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback

From: Pierre Morel
Date: Wed May 16 2018 - 03:31:00 EST

On 07/05/2018 17:11, Tony Krowiak wrote:
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. With access to this structure the driver will:

1. Ensure that only one mediated device is opened for the guest

2. Configure access to the AP devices for the guest.

Access to AP adapters, usage domains and control domains
is controlled by three bit masks contained in 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 Mask (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@xxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/kvm-ap.h | 21 ++++++++++
arch/s390/include/asm/kvm_host.h | 1 +
arch/s390/kvm/kvm-ap.c | 19 +++++++++
drivers/s390/crypto/vfio_ap_ops.c | 68 +++++++++++++++++++++++++++++++++
drivers/s390/crypto/vfio_ap_private.h | 2 +
5 files changed, 111 insertions(+), 0 deletions(-)

diff --git a/arch/s390/include/asm/kvm-ap.h b/arch/s390/include/asm/kvm-ap.h
index 21fe9f2..68c5a67 100644
--- a/arch/s390/include/asm/kvm-ap.h
+++ b/arch/s390/include/asm/kvm-ap.h
@@ -83,6 +83,27 @@ struct kvm_ap_matrix {
bool kvm_ap_instructions_available(void);

/**
+ * kvm_ap_refcount_read
+ *
+ * Read the AP reference count and return it.
+ */
+int kvm_ap_refcount_read(struct kvm *kvm);
+
+/**
+ * kvm_ap_refcount_inc
+ *
+ * Increment the AP reference count.
+ */
+void kvm_ap_refcount_inc(struct kvm *kvm);
+
+/**
+ * kvm_ap_refcount_dec
+ *
+ * Decrement the AP reference count
+ */
+void kvm_ap_refcount_dec(struct kvm *kvm);
+
+/**
* kvm_ap_configure_matrix
*
* Configure the AP matrix for a KVM guest.
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 8736cde..5f1ad02 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -717,6 +717,7 @@ struct kvm_s390_crypto {
__u8 aes_kw;
__u8 dea_kw;
__u8 apie;
+ atomic_t aprefs;
};

#define APCB0_MASK_SIZE 1
diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
index 98b53c7..848fb37 100644
--- a/arch/s390/kvm/kvm-ap.c
+++ b/arch/s390/kvm/kvm-ap.c
@@ -9,6 +9,7 @@
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <asm/kvm-ap.h>
+#include <asm/atomic.h>

#include "kvm-s390.h"

@@ -218,6 +219,24 @@ static int kvm_ap_validate_queue_sharing(struct kvm *kvm,
return 0;
}

+int kvm_ap_refcount_read(struct kvm *kvm)
+{
+ return atomic_read(&kvm->arch.crypto.aprefs);
+}
+EXPORT_SYMBOL(kvm_ap_refcount_read);
+
+void kvm_ap_refcount_inc(struct kvm *kvm)
+{
+ atomic_inc(&kvm->arch.crypto.aprefs);
+}
+EXPORT_SYMBOL(kvm_ap_refcount_inc);
+
+void kvm_ap_refcount_dec(struct kvm *kvm)
+{
+ atomic_dec(&kvm->arch.crypto.aprefs);
+}
+EXPORT_SYMBOL(kvm_ap_refcount_dec);

Why are these functions inside kvm-ap ?
Will anyone use this outer of vfio-ap ?

+
int kvm_ap_configure_matrix(struct kvm *kvm, struct kvm_ap_matrix *matrix)
{
int ret = 0;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 81e03b8..8866b0e 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -11,6 +11,8 @@
#include <linux/device.h>
#include <linux/list.h>
#include <linux/ctype.h>
+#include <linux/module.h>
+#include <asm/kvm-ap.h>

#include "vfio_ap_private.h"

@@ -47,6 +49,70 @@ 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;
+
+ if (!try_module_get(THIS_MODULE))
+ return -ENODEV;
+
+ 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;
+
+ /* Only one mediated device allowed per guest */
+ if (kvm_ap_refcount_read(matrix_mdev->kvm) != 0) {
+ ret = -EEXIST;
+ goto out_err;
+ }

Testing the existence should be the first thing to do.

+
+ kvm_ap_refcount_inc(matrix_mdev->kvm);
+
+ ret = kvm_ap_configure_matrix(matrix_mdev->kvm, &matrix_mdev->matrix);
+ if (ret)
+ goto config_err;
+
+ return 0;
+
+config_err:
+ kvm_ap_refcount_dec(matrix_mdev->kvm);
+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);
+
+ kvm_ap_deconfigure_matrix(matrix_mdev->kvm);
+ vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
+ &matrix_mdev->group_notifier);
+ kvm_ap_refcount_dec(matrix_mdev->kvm);
+ module_put(THIS_MODULE);
+}
+
static ssize_t name_show(struct kobject *kobj, struct device *dev, char *buf)
{
return sprintf(buf, "%s\n", VFIO_AP_MDEV_NAME_HWVIRT);
@@ -773,6 +839,8 @@ 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 8b6ad66..ab072e9 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -32,6 +32,8 @@ 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 BÃblingen - Germany