gpu: host1x: Forbid unrelated SETCLASS opcode in the firewall

Several channels could be made to write the same unit concurrently via
the SETCLASS opcode, trusting userspace is a bad idea. It should be
possible to drop the per-client channel reservation and add a per-unit
locking by inserting MLOCK's to the command stream to re-allow the
SETCLASS opcode, but it will be much more work. Let's forbid the
unit-unrelated class changes for now.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Erik Faye-Lund <kusmabite@gmail.com>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/drm.c

@@ -532,6 +532,7 @@ int tegra_drm_submit(struct tegra_drm_context *context,
 	}
 
 	job->is_addr_reg = context->client->ops->is_addr_reg;
+	job->is_valid_class = context->client->ops->is_valid_class;
 	job->syncpt_incrs = syncpt.incrs;
 	job->syncpt_id = syncpt.id;
 	job->timeout = 10000;

drivers/gpu/drm/tegra/drm.h

@@ -83,6 +83,7 @@ struct tegra_drm_client_ops {
 			    struct tegra_drm_context *context);
 	void (*close_channel)(struct tegra_drm_context *context);
 	int (*is_addr_reg)(struct device *dev, u32 class, u32 offset);
+	int (*is_valid_class)(u32 class);
 	int (*submit)(struct tegra_drm_context *context,
 		      struct drm_tegra_submit *args, struct drm_device *drm,
 		      struct drm_file *file);

drivers/gpu/drm/tegra/gr2d.c

@@ -109,10 +109,17 @@ static int gr2d_is_addr_reg(struct device *dev, u32 class, u32 offset)
 	return 0;
 }
 
+static int gr2d_is_valid_class(u32 class)
+{
+	return (class == HOST1X_CLASS_GR2D ||
+		class == HOST1X_CLASS_GR2D_SB);
+}
+
 static const struct tegra_drm_client_ops gr2d_ops = {
 	.open_channel = gr2d_open_channel,
 	.close_channel = gr2d_close_channel,
 	.is_addr_reg = gr2d_is_addr_reg,
+	.is_valid_class = gr2d_is_valid_class,
 	.submit = tegra_drm_submit,
 };