cmd: add subcommand cpu-features to dump supported CPU features

This patch adds the subcommand cpu-features, used for retrieving the
features supported by the current physical machine's CPU.

Signed-off-by: Tianyu Zhou <[email protected]>

Author: tianyuzhou95

runsc/cli/main.go

@@ -280,6 +280,7 @@ func forEachCmd(cb func(cmd subcommands.Command, group string)) {
 	cb(new(cmd.Uninstall), helperGroup)
 	cb(new(nvproxy.Nvproxy), helperGroup)
 	cb(new(trace.Trace), helperGroup)
+	cb(new(cmd.CPUFeatures), helperGroup)
 
 	const debugGroup = "debug"
 	cb(new(cmd.Debug), debugGroup)

runsc/cmd/BUILD

@@ -39,6 +39,7 @@ go_library(
         "chroot.go",
         "cmd.go",
         "create.go",
+        "cpu_features.go",
         "debug.go",
         "delete.go",
         "do.go",

runsc/cmd/cpu_features.go

@@ -0,0 +1,63 @@
+// Copyright 2025 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/google/subcommands"
+	"gvisor.dev/gvisor/pkg/cpuid"
+	"gvisor.dev/gvisor/runsc/flag"
+)
+
+// List implements subcommands.Command for the "cpu-features" command.
+type CPUFeatures struct{}
+
+// Name implements subcommands.command.name.
+func (*CPUFeatures) Name() string {
+	return "cpu-features"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*CPUFeatures) Synopsis() string {
+	return "list CPU features supported on current machine"
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*CPUFeatures) Usage() string {
+	return "cpu-features\n"
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (*CPUFeatures) SetFlags(*flag.FlagSet) {}
+
+// Execute implements subcommands.Command.Execute.
+func (*CPUFeatures) Execute(_ context.Context, _ *flag.FlagSet, args ...any) subcommands.ExitStatus {
+	cpuid.Initialize()
+	hfs := cpuid.HostFeatureSet().Fixed()
+	allFeatures := cpuid.AllFeatures()
+
+	features := []string{}
+	for _, v := range allFeatures {
+		if hfs.HasFeature(v) {
+			features = append(features, v.String())
+		}
+	}
+	fmt.Println(strings.Join(features, ","))
+
+	return subcommands.ExitSuccess
+}