drm/msm: Add opt-in for VM_BIND

Add a SET_PARAM for userspace to request to manage to the VM itself,
instead of getting a kernel managed VM.

In order to transition to a userspace managed VM, this param must be set
before any mappings are created.

Signed-off-by: Rob Clark <[email protected]>
Signed-off-by: Rob Clark <[email protected]>
Tested-by: Antonino Maniscalco <[email protected]>
Reviewed-by: Antonino Maniscalco <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/661494/

Author: robclark

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

@@ -2276,7 +2276,7 @@ a6xx_create_vm(struct msm_gpu *gpu, struct platform_device *pdev)
 }
 
 static struct drm_gpuvm *
-a6xx_create_private_vm(struct msm_gpu *gpu)
+a6xx_create_private_vm(struct msm_gpu *gpu, bool kernel_managed)
 {
 	struct msm_mmu *mmu;
 
@@ -2286,7 +2286,7 @@ a6xx_create_private_vm(struct msm_gpu *gpu)
 		return ERR_CAST(mmu);
 
 	return msm_gem_vm_create(gpu->dev, mmu, "gpu", ADRENO_VM_START,
-				 adreno_private_vm_size(gpu), true);
+				 adreno_private_vm_size(gpu), kernel_managed);
 }
 
 static uint32_t a6xx_get_rptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)

drivers/gpu/drm/msm/adreno/adreno_gpu.c

@@ -504,6 +504,21 @@ int adreno_set_param(struct msm_gpu *gpu, struct msm_context *ctx,
 		if (!capable(CAP_SYS_ADMIN))
 			return UERR(EPERM, drm, "invalid permissions");
 		return msm_context_set_sysprof(ctx, gpu, value);
+	case MSM_PARAM_EN_VM_BIND:
+		/* We can only support VM_BIND with per-process pgtables: */
+		if (ctx->vm == gpu->vm)
+			return UERR(EINVAL, drm, "requires per-process pgtables");
+
+		/*
+		 * We can only swtich to VM_BIND mode if the VM has not yet
+		 * been created:
+		 */
+		if (ctx->vm)
+			return UERR(EBUSY, drm, "VM already created");
+
+		ctx->userspace_managed_vm = value;
+
+		return 0;
 	default:
 		return UERR(EINVAL, drm, "%s: invalid param: %u", gpu->name, param);
 	}

drivers/gpu/drm/msm/msm_drv.c

@@ -232,9 +232,21 @@ static void load_gpu(struct drm_device *dev)
  */
 struct drm_gpuvm *msm_context_vm(struct drm_device *dev, struct msm_context *ctx)
 {
+	static DEFINE_MUTEX(init_lock);
 	struct msm_drm_private *priv = dev->dev_private;
-	if (!ctx->vm)
-		ctx->vm = msm_gpu_create_private_vm(priv->gpu, current);
+
+	/* Once ctx->vm is created it is valid for the lifetime of the context: */
+	if (ctx->vm)
+		return ctx->vm;
+
+	mutex_lock(&init_lock);
+	if (!ctx->vm) {
+		ctx->vm = msm_gpu_create_private_vm(
+			priv->gpu, current, !ctx->userspace_managed_vm);
+
+	}
+	mutex_unlock(&init_lock);
+
 	return ctx->vm;
 }
 
@@ -424,6 +436,9 @@ static int msm_ioctl_gem_info_iova(struct drm_device *dev,
 	if (!priv->gpu)
 		return -EINVAL;
 
+	if (msm_context_is_vmbind(ctx))
+		return UERR(EINVAL, dev, "VM_BIND is enabled");
+
 	if (should_fail(&fail_gem_iova, obj->size))
 		return -ENOMEM;
 
@@ -445,6 +460,9 @@ static int msm_ioctl_gem_info_set_iova(struct drm_device *dev,
 	if (!priv->gpu)
 		return -EINVAL;
 
+	if (msm_context_is_vmbind(ctx))
+		return UERR(EINVAL, dev, "VM_BIND is enabled");
+
 	/* Only supported if per-process address space is supported: */
 	if (priv->gpu->vm == vm)
 		return UERR(EOPNOTSUPP, dev, "requires per-process pgtables");

drivers/gpu/drm/msm/msm_gem.c

@@ -81,6 +81,14 @@ static void msm_gem_close(struct drm_gem_object *obj, struct drm_file *file)
 	if (!ctx->vm)
 		return;
 
+	/*
+	 * VM_BIND does not depend on implicit teardown of VMAs on handle
+	 * close, but instead on implicit teardown of the VM when the device
+	 * is closed (see msm_gem_vm_close())
+	 */
+	if (msm_context_is_vmbind(ctx))
+		return;
+
 	/*
 	 * TODO we might need to kick this to a queue to avoid blocking
 	 * in CLOSE ioctl

drivers/gpu/drm/msm/msm_gpu.c

@@ -829,7 +829,8 @@ static int get_clocks(struct platform_device *pdev, struct msm_gpu *gpu)
 
 /* Return a new address space for a msm_drm_private instance */
 struct drm_gpuvm *
-msm_gpu_create_private_vm(struct msm_gpu *gpu, struct task_struct *task)
+msm_gpu_create_private_vm(struct msm_gpu *gpu, struct task_struct *task,
+			  bool kernel_managed)
 {
 	struct drm_gpuvm *vm = NULL;
 
@@ -841,7 +842,7 @@ msm_gpu_create_private_vm(struct msm_gpu *gpu, struct task_struct *task)
 	 * the global one
 	 */
 	if (gpu->funcs->create_private_vm) {
-		vm = gpu->funcs->create_private_vm(gpu);
+		vm = gpu->funcs->create_private_vm(gpu, kernel_managed);
 		if (!IS_ERR(vm))
 			to_msm_vm(vm)->pid = get_pid(task_pid(task));
 	}

drivers/gpu/drm/msm/msm_gpu.h

@@ -79,7 +79,7 @@ struct msm_gpu_funcs {
 	void (*gpu_set_freq)(struct msm_gpu *gpu, struct dev_pm_opp *opp,
 			     bool suspended);
 	struct drm_gpuvm *(*create_vm)(struct msm_gpu *gpu, struct platform_device *pdev);
-	struct drm_gpuvm *(*create_private_vm)(struct msm_gpu *gpu);
+	struct drm_gpuvm *(*create_private_vm)(struct msm_gpu *gpu, bool kernel_managed);
 	uint32_t (*get_rptr)(struct msm_gpu *gpu, struct msm_ringbuffer *ring);
 
 	/**
@@ -364,6 +364,14 @@ struct msm_context {
 	 */
 	bool closed;
 
+	/**
+	 * @userspace_managed_vm:
+	 *
+	 * Has userspace opted-in to userspace managed VM (ie. VM_BIND) via
+	 * MSM_PARAM_EN_VM_BIND?
+	 */
+	bool userspace_managed_vm;
+
 	/**
 	 * @vm:
 	 *
@@ -456,6 +464,22 @@ struct msm_context {
 
 struct drm_gpuvm *msm_context_vm(struct drm_device *dev, struct msm_context *ctx);
 
+/**
+ * msm_context_is_vm_bind() - has userspace opted in to VM_BIND?
+ *
+ * @ctx: the drm_file context
+ *
+ * See MSM_PARAM_EN_VM_BIND.  If userspace is managing the VM, it can
+ * do sparse binding including having multiple, potentially partial,
+ * mappings in the VM.  Therefore certain legacy uabi (ie. GET_IOVA,
+ * SET_IOVA) are rejected because they don't have a sensible meaning.
+ */
+static inline bool
+msm_context_is_vmbind(struct msm_context *ctx)
+{
+	return ctx->userspace_managed_vm;
+}
+
 /**
  * msm_gpu_convert_priority - Map userspace priority to ring # and sched priority
  *
@@ -683,7 +707,8 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev,
 		const char *name, struct msm_gpu_config *config);
 
 struct drm_gpuvm *
-msm_gpu_create_private_vm(struct msm_gpu *gpu, struct task_struct *task);
+msm_gpu_create_private_vm(struct msm_gpu *gpu, struct task_struct *task,
+			  bool kernel_managed);
 
 void msm_gpu_cleanup(struct msm_gpu *gpu);
 

include/uapi/drm/msm_drm.h

@@ -93,6 +93,30 @@ struct drm_msm_timespec {
 #define MSM_PARAM_UCHE_TRAP_BASE 0x14 /* RO */
 /* PRR (Partially Resident Region) is required for sparse residency: */
 #define MSM_PARAM_HAS_PRR    0x15  /* RO */
+/* MSM_PARAM_EN_VM_BIND is set to 1 to enable VM_BIND ops.
+ *
+ * With VM_BIND enabled, userspace is required to allocate iova and use the
+ * VM_BIND ops for map/unmap ioctls.  MSM_INFO_SET_IOVA and MSM_INFO_GET_IOVA
+ * will be rejected.  (The latter does not have a sensible meaning when a BO
+ * can have multiple and/or partial mappings.)
+ *
+ * With VM_BIND enabled, userspace does not include a submit_bo table in the
+ * SUBMIT ioctl (this will be rejected), the resident set is determined by
+ * the the VM_BIND ops.
+ *
+ * Enabling VM_BIND will fail on devices which do not have per-process pgtables.
+ * And it is not allowed to disable VM_BIND once it has been enabled.
+ *
+ * Enabling VM_BIND should be done (attempted) prior to allocating any BOs or
+ * submitqueues of type MSM_SUBMITQUEUE_VM_BIND.
+ *
+ * Relatedly, when VM_BIND mode is enabled, the kernel will not try to recover
+ * from GPU faults or failed async VM_BIND ops, in particular because it is
+ * difficult to communicate to userspace which op failed so that userspace
+ * could rewind and try again.  When the VM is marked unusable, the SUBMIT
+ * ioctl will throw -EPIPE.
+ */
+#define MSM_PARAM_EN_VM_BIND 0x16  /* WO, once */
 
 /* For backwards compat.  The original support for preemption was based on
  * a single ring per priority level so # of priority levels equals the #