[RFC PATCH v3 10/20] vfio/pci: Use access ops for runtime-PM requests

[Shameer Kolothum <skolothumtho@nvidia.com>]

Userspace low-power requests change PM references and device mappings.
Run these requests through access ops so recovery can reject new
requests and drain admitted operations.

Validate userspace arguments and obtain the eventfd reference before
entering SRCU. Release the reference if entry fails. Keep the existing
memory_lock protection and PM reference handling.

Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
---
 drivers/vfio/pci/vfio_pci_core.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index fb7f46c2ca36..fc6b2673be88 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -454,9 +454,11 @@ int vfio_pci_try_set_power_state(struct vfio_pci_core_device *vdev,
 					pci_set_power_state);
 }
 
-static int vfio_pci_runtime_pm_entry(struct vfio_pci_core_device *vdev,
-				     struct eventfd_ctx *efdctx)
+static long vfio_pci_runtime_pm_entry(struct vfio_pci_core_device *vdev,
+				      void *data)
 {
+	struct eventfd_ctx *efdctx = data;
+
 	/*
 	 * The vdev power related flags are protected with 'memory_lock'
 	 * semaphore.
@@ -492,7 +494,7 @@ static int vfio_pci_core_pm_entry(struct vfio_pci_core_device *vdev, u32 flags,
 	 * while returning from the ioctl and then the device can go into
 	 * runtime suspended state.
 	 */
-	return vfio_pci_runtime_pm_entry(vdev, NULL);
+	return vfio_pci_core_access(vdev, vfio_pci_runtime_pm_entry, NULL);
 }
 
 static int vfio_pci_core_pm_entry_with_wakeup(
@@ -519,7 +521,7 @@ static int vfio_pci_core_pm_entry_with_wakeup(
 	if (IS_ERR(efdctx))
 		return PTR_ERR(efdctx);
 
-	ret = vfio_pci_runtime_pm_entry(vdev, efdctx);
+	ret = vfio_pci_core_access(vdev, vfio_pci_runtime_pm_entry, efdctx);
 	if (ret)
 		eventfd_ctx_put(efdctx);
 
@@ -552,6 +554,13 @@ static void vfio_pci_runtime_pm_exit(struct vfio_pci_core_device *vdev)
 	up_write(&vdev->memory_lock);
 }
 
+static long vfio_pci_access_pm_exit(struct vfio_pci_core_device *vdev,
+				    void *data)
+{
+	vfio_pci_runtime_pm_exit(vdev);
+	return 0;
+}
+
 static int vfio_pci_core_pm_exit(struct vfio_pci_core_device *vdev, u32 flags,
 				 void __user *arg, size_t argsz)
 {
@@ -568,8 +577,7 @@ static int vfio_pci_core_pm_exit(struct vfio_pci_core_device *vdev, u32 flags,
 	 * already signaled the eventfd and exited low power mode itself.
 	 * pm_runtime_engaged protects the redundant call here.
 	 */
-	vfio_pci_runtime_pm_exit(vdev);
-	return 0;
+	return vfio_pci_core_access(vdev, vfio_pci_access_pm_exit, NULL);
 }
 
 #ifdef CONFIG_PM
-- 
2.43.0