gpu: allow unsandboxed implicit render server spawn

Allow virglrenderer to implicitly spawn a render_server process when a
render_server_socket is not provided and sandboxing is disabled.

BUG=None
TEST=cargo build --features=gpu,x,wl-dmabuf,virgl_renderer,virgl_renderer_next

Change-Id: Icb682ffbf5812675d3c0c8e5a3d11006ecd53e8d
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4563457
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Ryan Neph <ryanneph@google.com>
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>

devices/src/virtio/gpu/mod.rs

@@ -1113,7 +1113,9 @@ impl Gpu {
             GpuMode::ModeGfxstream => RutabagaComponentType::Gfxstream,
         };
 
-        let use_render_server = rutabaga_server_descriptor.is_some();
+        // only allow virglrenderer to fork its own render server when crosvm sandboxing is disabled
+        let use_render_server = rutabaga_server_descriptor.is_some()
+            || gpu_parameters.allow_implicit_render_server_exec;
 
         let rutabaga_builder = RutabagaBuilder::new(component, gpu_parameters.capset_mask)
             .set_display_width(display_width)

devices/src/virtio/gpu/parameters.rs

@@ -67,6 +67,7 @@ pub struct GpuParameters {
     // enforce that blob resources MUST be exportable as file descriptors
     pub external_blob: bool,
     pub system_blob: bool,
+    pub allow_implicit_render_server_exec: bool,
 }
 
 impl Default for GpuParameters {
@@ -89,6 +90,7 @@ impl Default for GpuParameters {
             capset_mask: 0,
             external_blob: false,
             system_blob: false,
+            allow_implicit_render_server_exec: false,
         }
     }
 }

src/crosvm/sys/unix/gpu.rs

@@ -93,6 +93,7 @@ pub fn create_gpu_device(
     let is_sandboxed = cfg.jail_config.is_some();
     let mut gpu_params = cfg.gpu_parameters.clone().unwrap();
     gpu_params.external_blob = is_sandboxed;
+    gpu_params.allow_implicit_render_server_exec = !is_sandboxed;
 
     let mut display_backends = vec![
         virtio::DisplayBackend::X(cfg.x_display.clone()),