[RFC PATCH v2 1/2] s390/vfio-ap: Signal eventfd when guest AP configuration is changed

Rorie Reyes
2025-02-25T20:12:17Z

In this patch, an eventfd object is created by the vfio_ap device driver
and used to notify userspace when a guests's AP configuration is
dynamically changed. Such changes may occur whenever:

* An adapter, domain or control domain is assigned to or unassigned from a
mediated device that is attached to the guest.
* A queue assigned to the mediated device that is attached to a guest is
bound to or unbound from the vfio_ap device driver. This can occur
either by manually binding/unbinding the queue via the vfio_ap driver's
sysfs bind/unbind attribute interfaces, or because an adapter, domain or
control domain assigned to the mediated device is added to or removed
from the host's AP configuration via an SE/HMC

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
Reviewed-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Tested-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
drivers/s390/crypto/vfio_ap_ops.c | 52 ++++++++++++++++++++++++++-
drivers/s390/crypto/vfio_ap_private.h | 2 ++
include/uapi/linux/vfio.h | 1 +
3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index a52c2690933f..c6ff4ab13f16 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -650,13 +650,22 @@ static void vfio_ap_matrix_init(struct ap_config_info *info,
matrix->adm_max = info->apxa ? info->nd : 15;
}

+static void signal_guest_ap_cfg_changed(struct ap_matrix_mdev *matrix_mdev)
+{
+ if (matrix_mdev->cfg_chg_trigger)
+ eventfd_signal(matrix_mdev->cfg_chg_trigger);
+}
+
static void vfio_ap_mdev_update_guest_apcb(struct ap_matrix_mdev *matrix_mdev)
{
- if (matrix_mdev->kvm)
+ if (matrix_mdev->kvm) {
kvm_arch_crypto_set_masks(matrix_mdev->kvm,
matrix_mdev->shadow_apcb.apm,
matrix_mdev->shadow_apcb.aqm,
matrix_mdev->shadow_apcb.adm);
+
+ signal_guest_ap_cfg_changed(matrix_mdev);
+ }
}

static bool vfio_ap_mdev_filter_cdoms(struct ap_matrix_mdev *matrix_mdev)
@@ -792,6 +801,7 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
if (ret)
goto err_put_vdev;
matrix_mdev->req_trigger = NULL;
+ matrix_mdev->cfg_chg_trigger = NULL;
dev_set_drvdata(&mdev->dev, matrix_mdev);
mutex_lock(&matrix_dev->mdevs_lock);
list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
@@ -1860,6 +1870,7 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
get_update_locks_for_kvm(kvm);

kvm_arch_crypto_clear_masks(kvm);
+ signal_guest_ap_cfg_changed(matrix_mdev);
vfio_ap_mdev_reset_queues(matrix_mdev);
kvm_put_kvm(kvm);
matrix_mdev->kvm = NULL;
@@ -2097,6 +2108,10 @@ static ssize_t vfio_ap_get_irq_info(unsigned long arg)
info.count = 1;
info.flags = VFIO_IRQ_INFO_EVENTFD;
break;
+ case VFIO_AP_CFG_CHG_IRQ_INDEX:
+ info.count = 1;
+ info.flags = VFIO_IRQ_INFO_EVENTFD;
+ break;
default:
return -EINVAL;
}
@@ -2160,6 +2175,39 @@ static int vfio_ap_set_request_irq(struct ap_matrix_mdev *matrix_mdev,
return 0;
}

+static int vfio_ap_set_cfg_change_irq(struct ap_matrix_mdev *matrix_mdev, unsigned long arg)
+{
+ s32 fd;
+ void __user *data;
+ unsigned long minsz;
+ struct eventfd_ctx *cfg_chg_trigger;
+
+ minsz = offsetofend(struct vfio_irq_set, count);
+ data = (void __user *)(arg + minsz);
+
+ if (get_user(fd, (s32 __user *)data))
+ return -EFAULT;
+
+ if (fd == -1) {
+ if (matrix_mdev->cfg_chg_trigger)
+ eventfd_ctx_put(matrix_mdev->cfg_chg_trigger);
+ matrix_mdev->cfg_chg_trigger = NULL;
+ } else if (fd >= 0) {
+ cfg_chg_trigger = eventfd_ctx_fdget(fd);
+ if (IS_ERR(cfg_chg_trigger))
+ return PTR_ERR(cfg_chg_trigger);
+
+ if (matrix_mdev->cfg_chg_trigger)
+ eventfd_ctx_put(matrix_mdev->cfg_chg_trigger);
+
+ matrix_mdev->cfg_chg_trigger = cfg_chg_trigger;
+ } else {
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int vfio_ap_set_irqs(struct ap_matrix_mdev *matrix_mdev,
unsigned long arg)
{
@@ -2175,6 +2223,8 @@ static int vfio_ap_set_irqs(struct ap_matrix_mdev *matrix_mdev,
switch (irq_set.index) {
case VFIO_AP_REQ_IRQ_INDEX:
return vfio_ap_set_request_irq(matrix_mdev, arg);
+ case VFIO_AP_CFG_CHG_IRQ_INDEX:
+ return vfio_ap_set_cfg_change_irq(matrix_mdev, arg);
default:
return -EINVAL;
}
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 437a161c8659..37de9c69b6eb 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -105,6 +105,7 @@ struct ap_queue_table {
* @mdev: the mediated device
* @qtable: table of queues (struct vfio_ap_queue) assigned to the mdev
* @req_trigger eventfd ctx for signaling userspace to return a device
+ * @cfg_chg_trigger eventfd ctx to signal AP config changed to userspace
* @apm_add: bitmap of APIDs added to the host's AP configuration
* @aqm_add: bitmap of APQIs added to the host's AP configuration
* @adm_add: bitmap of control domain numbers added to the host's AP
@@ -120,6 +121,7 @@ struct ap_matrix_mdev {
struct mdev_device *mdev;
struct ap_queue_table qtable;
struct eventfd_ctx *req_trigger;
+ struct eventfd_ctx *cfg_chg_trigger;
DECLARE_BITMAP(apm_add, AP_DEVICES);
DECLARE_BITMAP(aqm_add, AP_DOMAINS);
DECLARE_BITMAP(adm_add, AP_DOMAINS);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index c8dbf8219c4f..a2d3e1ac6239 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -671,6 +671,7 @@ enum {
*/
enum {
VFIO_AP_REQ_IRQ_INDEX,
+ VFIO_AP_CFG_CHG_IRQ_INDEX,
VFIO_AP_NUM_IRQS
};

--
2.39.5 (Apple Git-154)