[PATCH 1/1] vfio: remove VFIO_GROUP_NOTIFY_SET_KVM

Matthew Rosato
2022-05-17T18:09:13Z

Rather than relying on a notifier for associating the KVM with
the group, let's assume that the association has already been
made prior to device_open. The first time a device is opened
associate the group KVM with the device.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
drivers/gpu/drm/i915/gvt/gvt.h | 2 -
drivers/gpu/drm/i915/gvt/kvmgt.c | 60 +++++------------------
drivers/s390/crypto/vfio_ap_ops.c | 35 +++-----------
drivers/s390/crypto/vfio_ap_private.h | 3 --
drivers/vfio/vfio.c | 68 +++++++++------------------
include/linux/vfio.h | 5 +-
6 files changed, 41 insertions(+), 132 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h
index 2af4c83e733c..633acfcf76bf 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.h
+++ b/drivers/gpu/drm/i915/gvt/gvt.h
@@ -227,8 +227,6 @@ struct intel_vgpu {
struct mutex cache_lock;

struct notifier_block iommu_notifier;
- struct notifier_block group_notifier;
- struct kvm *kvm;
struct work_struct release_work;
atomic_t released;

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 7655ffa97d51..b317ae4cc7d2 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -761,23 +761,6 @@ static int intel_vgpu_iommu_notifier(struct notifier_block *nb,
return NOTIFY_OK;
}

-static int intel_vgpu_group_notifier(struct notifier_block *nb,
- unsigned long action, void *data)
-{
- struct intel_vgpu *vgpu =
- container_of(nb, struct intel_vgpu, group_notifier);
-
- /* the only action we care about */
- if (action == VFIO_GROUP_NOTIFY_SET_KVM) {
- vgpu->kvm = data;
-
- if (!data)
- schedule_work(&vgpu->release_work);
- }
-
- return NOTIFY_OK;
-}
-
static bool __kvmgt_vgpu_exist(struct intel_vgpu *vgpu)
{
struct intel_vgpu *itr;
@@ -789,7 +772,7 @@ static bool __kvmgt_vgpu_exist(struct intel_vgpu *vgpu)
if (!itr->attached)
continue;

- if (vgpu->kvm == itr->kvm) {
+ if (vgpu->vfio_device.kvm == itr->vfio_device.kvm) {
ret = true;
goto out;
}
@@ -806,7 +789,6 @@ static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
int ret;

vgpu->iommu_notifier.notifier_call = intel_vgpu_iommu_notifier;
- vgpu->group_notifier.notifier_call = intel_vgpu_group_notifier;

events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
ret = vfio_register_notifier(vfio_dev, VFIO_IOMMU_NOTIFY, &events,
@@ -817,38 +799,30 @@ static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
goto out;
}

- events = VFIO_GROUP_NOTIFY_SET_KVM;
- ret = vfio_register_notifier(vfio_dev, VFIO_GROUP_NOTIFY, &events,
- &vgpu->group_notifier);
- if (ret != 0) {
- gvt_vgpu_err("vfio_register_notifier for group failed: %d\n",
- ret);
- goto undo_iommu;
- }
-
ret = -EEXIST;
if (vgpu->attached)
- goto undo_register;
+ goto undo_iommu;

ret = -ESRCH;
- if (!vgpu->kvm || vgpu->kvm->mm != current->mm) {
+ if (!vgpu->vfio_device.kvm ||
+ vgpu->vfio_device.kvm->mm != current->mm) {
gvt_vgpu_err("KVM is required to use Intel vGPU\n");
- goto undo_register;
+ goto undo_iommu;
}

ret = -EEXIST;
if (__kvmgt_vgpu_exist(vgpu))
- goto undo_register;
+ goto undo_iommu;

vgpu->attached = true;
- kvm_get_kvm(vgpu->kvm);

kvmgt_protect_table_init(vgpu);
gvt_cache_init(vgpu);

vgpu->track_node.track_write = kvmgt_page_track_write;
vgpu->track_node.track_flush_slot = kvmgt_page_track_flush_slot;
- kvm_page_track_register_notifier(vgpu->kvm, &vgpu->track_node);
+ kvm_page_track_register_notifier(vgpu->vfio_device.kvm,
+ &vgpu->track_node);

debugfs_create_ulong(KVMGT_DEBUGFS_FILENAME, 0444, vgpu->debugfs,
&vgpu->nr_cache_entries);
@@ -858,10 +832,6 @@ static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
atomic_set(&vgpu->released, 0);
return 0;

-undo_register:
- vfio_unregister_notifier(vfio_dev, VFIO_GROUP_NOTIFY,
- &vgpu->group_notifier);
-
undo_iommu:
vfio_unregister_notifier(vfio_dev, VFIO_IOMMU_NOTIFY,
&vgpu->iommu_notifier);
@@ -898,21 +868,15 @@ static void __intel_vgpu_release(struct intel_vgpu *vgpu)
drm_WARN(&i915->drm, ret,
"vfio_unregister_notifier for iommu failed: %d\n", ret);

- ret = vfio_unregister_notifier(&vgpu->vfio_device, VFIO_GROUP_NOTIFY,
- &vgpu->group_notifier);
- drm_WARN(&i915->drm, ret,
- "vfio_unregister_notifier for group failed: %d\n", ret);
-
debugfs_remove(debugfs_lookup(KVMGT_DEBUGFS_FILENAME, vgpu->debugfs));

- kvm_page_track_unregister_notifier(vgpu->kvm, &vgpu->track_node);
- kvm_put_kvm(vgpu->kvm);
+ kvm_page_track_unregister_notifier(vgpu->vfio_device.kvm,
+ &vgpu->track_node);
kvmgt_protect_table_destroy(vgpu);
gvt_cache_destroy(vgpu);

intel_vgpu_release_msi_eventfd_ctx(vgpu);

- vgpu->kvm = NULL;
vgpu->attached = false;
}

@@ -1713,7 +1677,7 @@ static struct mdev_driver intel_vgpu_mdev_driver = {

int intel_gvt_page_track_add(struct intel_vgpu *info, u64 gfn)
{
- struct kvm *kvm = info->kvm;
+ struct kvm *kvm = info->vfio_device.kvm;
struct kvm_memory_slot *slot;
int idx;

@@ -1743,7 +1707,7 @@ int intel_gvt_page_track_add(struct intel_vgpu *info, u64 gfn)

int intel_gvt_page_track_remove(struct intel_vgpu *info, u64 gfn)
{
- struct kvm *kvm = info->kvm;
+ struct kvm *kvm = info->vfio_device.kvm;
struct kvm_memory_slot *slot;
int idx;

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index e8914024f5b1..43c68afe7e87 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -1284,25 +1284,6 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
}
}

-static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
- unsigned long action, void *data)
-{
- int notify_rc = NOTIFY_OK;
- struct ap_matrix_mdev *matrix_mdev;
-
- if (action != VFIO_GROUP_NOTIFY_SET_KVM)
- return NOTIFY_OK;
-
- matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier);
-
- if (!data)
- vfio_ap_mdev_unset_kvm(matrix_mdev);
- else if (vfio_ap_mdev_set_kvm(matrix_mdev, data))
- notify_rc = NOTIFY_DONE;
-
- return notify_rc;
-}
-
static struct vfio_ap_queue *vfio_ap_find_queue(int apqn)
{
struct device *dev;
@@ -1402,11 +1383,10 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
unsigned long events;
int ret;

- matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier;
- events = VFIO_GROUP_NOTIFY_SET_KVM;
+ if (!vdev->kvm)
+ return -EPERM;

- ret = vfio_register_notifier(vdev, VFIO_GROUP_NOTIFY, &events,
- &matrix_mdev->group_notifier);
+ ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
if (ret)
return ret;

@@ -1415,12 +1395,11 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY, &events,
&matrix_mdev->iommu_notifier);
if (ret)
- goto out_unregister_group;
+ goto err_kvm;
return 0;

-out_unregister_group:
- vfio_unregister_notifier(vdev, VFIO_GROUP_NOTIFY,
- &matrix_mdev->group_notifier);
+err_kvm:
+ vfio_ap_mdev_unset_kvm(matrix_mdev);
return ret;
}

@@ -1431,8 +1410,6 @@ static void vfio_ap_mdev_close_device(struct vfio_device *vdev)

vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY,
&matrix_mdev->iommu_notifier);
- vfio_unregister_notifier(vdev, VFIO_GROUP_NOTIFY,
- &matrix_mdev->group_notifier);
vfio_ap_mdev_unset_kvm(matrix_mdev);
}

diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 648fcaf8104a..a26efd804d0d 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -81,8 +81,6 @@ struct ap_matrix {
* @node: allows the ap_matrix_mdev struct to be added to a list
* @matrix: the adapters, usage domains and control domains assigned to the
* mediated matrix device.
- * @group_notifier: notifier block used for specifying callback function for
- * handling the VFIO_GROUP_NOTIFY_SET_KVM event
* @iommu_notifier: notifier block used for specifying callback function for
* handling the VFIO_IOMMU_NOTIFY_DMA_UNMAP even
* @kvm: the struct holding guest's state
@@ -94,7 +92,6 @@ struct ap_matrix_mdev {
struct vfio_device vdev;
struct list_head node;
struct ap_matrix matrix;
- struct notifier_block group_notifier;
struct notifier_block iommu_notifier;
struct kvm *kvm;
crypto_hook pqap_hook;
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index cfcff7764403..c5d421eda275 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -10,6 +10,7 @@
* Author: Tom Lyon, pugs@cisco.com
*/

+#include "linux/kvm_host.h"
#include <linux/cdev.h>
#include <linux/compat.h>
#include <linux/device.h>
@@ -1083,6 +1084,13 @@ static struct file *vfio_device_open(struct vfio_device *device)

mutex_lock(&device->dev_set->lock);
device->open_count++;
+ down_write(&device->group->group_rwsem);
+ if (device->open_count == 1 && device->group->kvm) {
+ device->kvm = device->group->kvm;
+ kvm_get_kvm(device->kvm);
+ }
+ up_write(&device->group->group_rwsem);
+
if (device->open_count == 1 && device->ops->open_device) {
ret = device->ops->open_device(device);
if (ret)
@@ -1123,6 +1131,12 @@ static struct file *vfio_device_open(struct vfio_device *device)
device->ops->close_device(device);
err_undo_count:
device->open_count--;
+ down_write(&device->group->group_rwsem);
+ if (device->open_count == 0 && device->kvm) {
+ kvm_put_kvm(device->kvm);
+ device->kvm = NULL;
+ }
+ up_write(&device->group->group_rwsem);
mutex_unlock(&device->dev_set->lock);
module_put(device->dev->driver->owner);
err_unassign_container:
@@ -1318,6 +1332,12 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
if (device->open_count == 1 && device->ops->close_device)
device->ops->close_device(device);
device->open_count--;
+ down_write(&device->group->group_rwsem);
+ if (device->open_count == 0 && device->kvm) {
+ kvm_put_kvm(device->kvm);
+ device->kvm = NULL;
+ }
+ up_write(&device->group->group_rwsem);
mutex_unlock(&device->dev_set->lock);

module_put(device->dev->driver->owner);
@@ -1726,8 +1746,8 @@ EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent);
* @file: VFIO group file
* @kvm: KVM to link
*
- * The kvm pointer will be forwarded to all the vfio_device's attached to the
- * VFIO file via the VFIO_GROUP_NOTIFY_SET_KVM notifier.
+ * When a VFIO device is first opened the KVM will be available in
+ * device->kvm if one was associated with the group.
*/
void vfio_file_set_kvm(struct file *file, struct kvm *kvm)
{
@@ -1738,8 +1758,6 @@ void vfio_file_set_kvm(struct file *file, struct kvm *kvm)

down_write(&group->group_rwsem);
group->kvm = kvm;
- blocking_notifier_call_chain(&group->notifier,
- VFIO_GROUP_NOTIFY_SET_KVM, kvm);
up_write(&group->group_rwsem);
}
EXPORT_SYMBOL_GPL(vfio_file_set_kvm);
@@ -2039,42 +2057,6 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
return ret;
}

-static int vfio_register_group_notifier(struct vfio_group *group,
- unsigned long *events,
- struct notifier_block *nb)
-{
- int ret;
- bool set_kvm = false;
-
- if (*events & VFIO_GROUP_NOTIFY_SET_KVM)
- set_kvm = true;
-
- /* clear known events */
- *events &= ~VFIO_GROUP_NOTIFY_SET_KVM;
-
- /* refuse to continue if still events remaining */
- if (*events)
- return -EINVAL;
-
- ret = blocking_notifier_chain_register(&group->notifier, nb);
- if (ret)
- return ret;
-
- /*
- * The attaching of kvm and vfio_group might already happen, so
- * here we replay once upon registration.
- */
- if (set_kvm) {
- down_read(&group->group_rwsem);
- if (group->kvm)
- blocking_notifier_call_chain(&group->notifier,
- VFIO_GROUP_NOTIFY_SET_KVM,
- group->kvm);
- up_read(&group->group_rwsem);
- }
- return 0;
-}
-
int vfio_register_notifier(struct vfio_device *device,
enum vfio_notify_type type, unsigned long *events,
struct notifier_block *nb)
@@ -2090,9 +2072,6 @@ int vfio_register_notifier(struct vfio_device *device,
case VFIO_IOMMU_NOTIFY:
ret = vfio_register_iommu_notifier(group, events, nb);
break;
- case VFIO_GROUP_NOTIFY:
- ret = vfio_register_group_notifier(group, events, nb);
- break;
default:
ret = -EINVAL;
}
@@ -2114,9 +2093,6 @@ int vfio_unregister_notifier(struct vfio_device *device,
case VFIO_IOMMU_NOTIFY:
ret = vfio_unregister_iommu_notifier(group, nb);
break;
- case VFIO_GROUP_NOTIFY:
- ret = blocking_notifier_chain_unregister(&group->notifier, nb);
- break;
default:
ret = -EINVAL;
}
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 45b287826ce6..5f691453e3fb 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -36,6 +36,7 @@ struct vfio_device {
struct vfio_device_set *dev_set;
struct list_head dev_set_list;
unsigned int migration_flags;
+ struct kvm *kvm;

/* Members below here are private, not for driver use */
refcount_t refcount;
@@ -155,15 +156,11 @@ extern int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova,
/* each type has independent events */
enum vfio_notify_type {
VFIO_IOMMU_NOTIFY = 0,
- VFIO_GROUP_NOTIFY = 1,
};

/* events for VFIO_IOMMU_NOTIFY */
#define VFIO_IOMMU_NOTIFY_DMA_UNMAP BIT(0)

-/* events for VFIO_GROUP_NOTIFY */
-#define VFIO_GROUP_NOTIFY_SET_KVM BIT(0)
-
extern int vfio_register_notifier(struct vfio_device *device,
enum vfio_notify_type type,
unsigned long *required_events,
--
2.27.0