vmm: Allow empty gpus list when gpu is not enabled

Author: kvinwang

vmm/rpc/src/lib.rs

@@ -7,3 +7,12 @@ extern crate alloc;
 pub use generated::*;
 
 mod generated;
+
+impl GpuConfig {
+    pub fn is_empty(&self) -> bool {
+        if self.attach_mode == "all" {
+            return false;
+        }
+        self.gpus.is_empty()
+    }
+}

vmm/src/main_service.rs

@@ -66,7 +66,7 @@ pub fn resolve_gpus_with_config(
     gpu_cfg: &rpc::GpuConfig,
     cvm_config: &crate::config::CvmConfig,
 ) -> Result<GpuConfig> {
-    if !cvm_config.gpu.enabled {
+    if !cvm_config.gpu.enabled && !gpu_cfg.is_empty() {
         bail!("GPU is not enabled");
     }
     let gpus = resolve_gpus(gpu_cfg)?;