drm/msm: Lazily create context VM

In the next commit, a way for userspace to opt-in to userspace managed
VM is added.  For this to work, we need to defer creation of the VM
until it is needed.

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/661490/

Author: robclark

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

@@ -112,6 +112,7 @@ static void a6xx_set_pagetable(struct a6xx_gpu *a6xx_gpu,
 {
 	bool sysprof = refcount_read(&a6xx_gpu->base.base.sysprof_active) > 1;
 	struct msm_context *ctx = submit->queue->ctx;
+	struct drm_gpuvm *vm = msm_context_vm(submit->dev, ctx);
 	struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
 	phys_addr_t ttbr;
 	u32 asid;
@@ -120,7 +121,7 @@ static void a6xx_set_pagetable(struct a6xx_gpu *a6xx_gpu,
 	if (ctx->seqno == ring->cur_ctx_seqno)
 		return;
 
-	if (msm_iommu_pagetable_params(to_msm_vm(ctx->vm)->mmu, &ttbr, &asid))
+	if (msm_iommu_pagetable_params(to_msm_vm(vm)->mmu, &ttbr, &asid))
 		return;
 
 	if (adreno_gpu->info->family >= ADRENO_7XX_GEN1) {

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

@@ -369,6 +369,8 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_context *ctx,
 {
 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 	struct drm_device *drm = gpu->dev;
+	/* Note ctx can be NULL when called from rd_open(): */
+	struct drm_gpuvm *vm = ctx ? msm_context_vm(drm, ctx) : NULL;
 
 	/* No pointer params yet */
 	if (*len != 0)
@@ -414,23 +416,23 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_context *ctx,
 		*value = 0;
 		return 0;
 	case MSM_PARAM_FAULTS:
-		if (ctx->vm)
-			*value = gpu->global_faults + to_msm_vm(ctx->vm)->faults;
+		if (vm)
+			*value = gpu->global_faults + to_msm_vm(vm)->faults;
 		else
 			*value = gpu->global_faults;
 		return 0;
 	case MSM_PARAM_SUSPENDS:
 		*value = gpu->suspend_count;
 		return 0;
 	case MSM_PARAM_VA_START:
-		if (ctx->vm == gpu->vm)
+		if (vm == gpu->vm)
 			return UERR(EINVAL, drm, "requires per-process pgtables");
-		*value = ctx->vm->mm_start;
+		*value = vm->mm_start;
 		return 0;
 	case MSM_PARAM_VA_SIZE:
-		if (ctx->vm == gpu->vm)
+		if (vm == gpu->vm)
 			return UERR(EINVAL, drm, "requires per-process pgtables");
-		*value = ctx->vm->mm_range;
+		*value = vm->mm_range;
 		return 0;
 	case MSM_PARAM_HIGHEST_BANK_BIT:
 		*value = adreno_gpu->ubwc_config.highest_bank_bit;

drivers/gpu/drm/msm/msm_drv.c

@@ -218,10 +218,29 @@ static void load_gpu(struct drm_device *dev)
 	mutex_unlock(&init_lock);
 }
 
+/**
+ * msm_context_vm - lazily create the context's VM
+ *
+ * @dev: the drm device
+ * @ctx: the context
+ *
+ * The VM is lazily created, so that userspace has a chance to opt-in to having
+ * a userspace managed VM before the VM is created.
+ *
+ * Note that this does not return a reference to the VM.  Once the VM is created,
+ * it exists for the lifetime of the context.
+ */
+struct drm_gpuvm *msm_context_vm(struct drm_device *dev, struct msm_context *ctx)
+{
+	struct msm_drm_private *priv = dev->dev_private;
+	if (!ctx->vm)
+		ctx->vm = msm_gpu_create_private_vm(priv->gpu, current);
+	return ctx->vm;
+}
+
 static int context_init(struct drm_device *dev, struct drm_file *file)
 {
 	static atomic_t ident = ATOMIC_INIT(0);
-	struct msm_drm_private *priv = dev->dev_private;
 	struct msm_context *ctx;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
@@ -234,7 +253,6 @@ static int context_init(struct drm_device *dev, struct drm_file *file)
 	kref_init(&ctx->ref);
 	msm_submitqueue_init(dev, ctx);
 
-	ctx->vm = msm_gpu_create_private_vm(priv->gpu, current);
 	file->driver_priv = ctx;
 
 	ctx->seqno = atomic_inc_return(&ident);
@@ -413,7 +431,7 @@ static int msm_ioctl_gem_info_iova(struct drm_device *dev,
 	 * Don't pin the memory here - just get an address so that userspace can
 	 * be productive
 	 */
-	return msm_gem_get_iova(obj, ctx->vm, iova);
+	return msm_gem_get_iova(obj, msm_context_vm(dev, ctx), iova);
 }
 
 static int msm_ioctl_gem_info_set_iova(struct drm_device *dev,
@@ -422,18 +440,19 @@ static int msm_ioctl_gem_info_set_iova(struct drm_device *dev,
 {
 	struct msm_drm_private *priv = dev->dev_private;
 	struct msm_context *ctx = file->driver_priv;
+	struct drm_gpuvm *vm = msm_context_vm(dev, ctx);
 
 	if (!priv->gpu)
 		return -EINVAL;
 
 	/* Only supported if per-process address space is supported: */
-	if (priv->gpu->vm == ctx->vm)
+	if (priv->gpu->vm == vm)
 		return UERR(EOPNOTSUPP, dev, "requires per-process pgtables");
 
 	if (should_fail(&fail_gem_iova, obj->size))
 		return -ENOMEM;
 
-	return msm_gem_set_iova(obj, ctx->vm, iova);
+	return msm_gem_set_iova(obj, vm, iova);
 }
 
 static int msm_ioctl_gem_info_set_metadata(struct drm_gem_object *obj,

drivers/gpu/drm/msm/msm_gem_submit.c

@@ -64,7 +64,7 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
 
 	kref_init(&submit->ref);
 	submit->dev = dev;
-	submit->vm = queue->ctx->vm;
+	submit->vm = msm_context_vm(dev, queue->ctx);
 	submit->gpu = gpu;
 	submit->cmd = (void *)&submit->bos[nr_bos];
 	submit->queue = queue;

drivers/gpu/drm/msm/msm_gpu.h

@@ -364,7 +364,12 @@ struct msm_context {
 	 */
 	bool closed;
 
-	/** @vm: the per-process GPU address-space */
+	/**
+	 * @vm:
+	 *
+	 * The per-process GPU address-space.  Do not access directly, use
+	 * msm_context_vm().
+	 */
 	struct drm_gpuvm *vm;
 
 	/** @kref: the reference count */
@@ -449,6 +454,8 @@ struct msm_context {
 	atomic64_t ctx_mem;
 };
 
+struct drm_gpuvm *msm_context_vm(struct drm_device *dev, struct msm_context *ctx);
+
 /**
  * msm_gpu_convert_priority - Map userspace priority to ring # and sched priority
  *