[PATCH v4 2/2] drm/amdgpu: Add CHANGE_ID option for USERQ ioctl

[David Francis <David.Francis@amd.com>]

Add a new option to the USERQ ioctl, which is called with
the queue_id of an existing user queue and an unused queue_id,
and changes that queue's id to the new value.

Calling with an invalid new handle will fail. Calling with new_handle
= handle will succeed if that queue exists but not do anything.

A poison queue object is inserted at the old handle during the
rekey to prevent concurrent FREE from destroying the queue or the
old id being reused mid-operation.

Performing this operation on a queue with signals or waits
outstanding is fine, as those hold not the queue_id but a
direct reference to the queue object.

v3: Poison queue and misc fixes

Signed-off-by: David Francis <David.Francis@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 60 +++++++++++++++++++++++
 include/uapi/drm/amdgpu_drm.h             | 17 +++++--
 2 files changed, 74 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index 32d1787aa7e2..699838042bda 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -35,6 +35,8 @@
 #include "amdgpu_userq_fence.h"
 #include "amdgpu_trace.h"
 
+struct amdgpu_usermode_queue poison_queue;
+
 u32 amdgpu_userq_get_supported_ip_mask(struct amdgpu_device *adev)
 {
 	int i;
@@ -852,6 +854,11 @@ static int amdgpu_userq_input_args_validate(struct drm_device *dev,
 		break;
 	case AMDGPU_USERQ_OP_LIST:
 		break;
+	case AMDGPU_USERQ_OP_CHANGE_ID:
+		if (!args->change_in.new_queue_id ||
+		    args->change_in.new_queue_id > AMDGPU_MAX_USERQ_COUNT)
+			return -EINVAL;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -1010,6 +1017,51 @@ amdgpu_userq_list(struct drm_file *filp, union drm_amdgpu_userq *args)
 	return ret;
 }
 
+static int amdgpu_userq_change_id(struct drm_file *filp, union drm_amdgpu_userq *args)
+{
+	struct amdgpu_fpriv *fpriv = filp->driver_priv;
+	struct amdgpu_userq_mgr *uq_mgr = &fpriv->userq_mgr;
+	struct amdgpu_usermode_queue *queue;
+	int ret = 0;
+
+	if (args->change_in.new_queue_id == args->change_in.queue_id) {
+		if (xa_load(&uq_mgr->userq_xa, args->change_in.queue_id))
+			return 0;
+		return -ENOENT;
+	}
+
+	/* Poison the old handle so it doesn't get freed or reused. */
+	queue = xa_store(&uq_mgr->userq_xa, args->change_in.queue_id, &poison_queue, GFP_KERNEL);
+	if (!queue) {
+		xa_erase(&uq_mgr->userq_xa, args->change_in.queue_id);
+		return -ENOENT;
+	}
+	if (queue == &poison_queue)
+		return -EINVAL;
+
+	ret = xa_insert(&uq_mgr->userq_xa, args->change_in.new_queue_id, queue, GFP_KERNEL);
+	if (ret == -EBUSY) {
+		queue = xa_store(&uq_mgr->userq_xa, args->change_in.queue_id, queue, GFP_KERNEL);
+		if (queue != &poison_queue) {
+			drm_err_once(adev_to_drm(uq_mgr->adev),
+				     "Expected poison queue to remain untouched during userqueue change id");
+			return -EINVAL;
+		}
+	}
+	if (ret == -ENOMEM)
+		return -ENOMEM;
+
+	/* remove the poison */
+	queue = xa_erase(&uq_mgr->userq_xa, args->change_in.queue_id);
+	if (queue != &poison_queue) {
+		drm_err_once(adev_to_drm(uq_mgr->adev),
+			     "Expected poison queue to remain untouched during userqueue change id");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 bool amdgpu_userq_enabled(struct drm_device *dev)
 {
 	struct amdgpu_device *adev = drm_to_adev(dev);
@@ -1046,6 +1098,11 @@ int amdgpu_userq_ioctl(struct drm_device *dev, void *data,
 
 	case AMDGPU_USERQ_OP_FREE:
 		xa_lock(&fpriv->userq_mgr.userq_xa);
+		queue = xa_load(&fpriv->userq_mgr.userq_xa, args->in.queue_id);
+		if (queue == &poison_queue) {
+			xa_unlock(&fpriv->userq_mgr.userq_xa);
+			return -EINVAL;
+		}
 		queue = __xa_erase(&fpriv->userq_mgr.userq_xa, args->in.queue_id);
 		xa_unlock(&fpriv->userq_mgr.userq_xa);
 		if (!queue)
@@ -1056,6 +1113,9 @@ int amdgpu_userq_ioctl(struct drm_device *dev, void *data,
 	case AMDGPU_USERQ_OP_LIST:
 		r = amdgpu_userq_list(filp, args);
 		break;
+	case AMDGPU_USERQ_OP_CHANGE_ID:
+		r = amdgpu_userq_change_id(filp, args);
+		break;
 	default:
 		drm_dbg_driver(dev, "Invalid user queue op specified: %d\n", args->in.op);
 		return -EINVAL;
diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
index 92738d630eea..37d0efd1eda4 100644
--- a/include/uapi/drm/amdgpu_drm.h
+++ b/include/uapi/drm/amdgpu_drm.h
@@ -330,9 +330,10 @@ union drm_amdgpu_ctx {
 };
 
 /* user queue IOCTL operations */
-#define AMDGPU_USERQ_OP_CREATE	1
-#define AMDGPU_USERQ_OP_FREE	2
-#define AMDGPU_USERQ_OP_LIST	3
+#define AMDGPU_USERQ_OP_CREATE		1
+#define AMDGPU_USERQ_OP_FREE		2
+#define AMDGPU_USERQ_OP_LIST		3
+#define AMDGPU_USERQ_OP_CHANGE_ID	4
 
 /* queue priority levels */
 /* low < normal low < normal high < high */
@@ -464,10 +465,20 @@ struct drm_amdgpu_userq_list_in_out {
 	__u64   entries;
 };
 
+struct drm_amdgpu_userq_change_id_in {
+	/** AMDGPU_USERQ_OP_CHANGE_ID */
+	__u32   op;
+	/** Queue id of some queue */
+	__u32   queue_id;
+	/** Queue id to change that queue to */
+	__u32   new_queue_id;
+};
+
 union drm_amdgpu_userq {
 	struct drm_amdgpu_userq_in in;
 	struct drm_amdgpu_userq_out out;
 	struct drm_amdgpu_userq_list_in_out list_in_out;
+	struct drm_amdgpu_userq_change_id_in change_in;
 };
 
 /* GFX V11 IP specific MQD parameters */
-- 
2.34.1