From 4dcbbc934dfa0097ca0039756231bbb4713811e0 Mon Sep 17 00:00:00 2001
From: dawn <dawn@tangled.org>
Date: Fri, 19 Jun 2026 23:10:36 +0300
Subject: [PATCH] spindle/microvm: use consistent qmp sock paths to avoid the
 AF_UNIX path limit

Signed-off-by: dawn <dawn@tangled.org>
---
 docker-compose.yml              |  4 ++++
 spindle/engines/microvm/qemu.go | 24 +++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/docker-compose.yml b/docker-compose.yml
index ad99a93c..1a0572c3 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -151,6 +151,10 @@ services:
       SPINDLE_MICROVM_PIPELINES_OVERLAY_DIR: /var/lib/spindle/overlays
       SPINDLE_MICROVM_PIPELINES_AGENT_PORT: "11240"
       SPINDLE_S3_LOG_BUCKET: ""
+      SPINDLE_MICROVM_PIPELINES_ENABLE_CGROUPS: "false"
+    # these two are required for cgroups, uncomment if testing
+    # privileged: true
+    # cgroup: host
     devices:
       - /dev/vsock:/dev/vsock
       - /dev/kvm:/dev/kvm
diff --git a/spindle/engines/microvm/qemu.go b/spindle/engines/microvm/qemu.go
index 0d1fe255..b8502506 100644
--- a/spindle/engines/microvm/qemu.go
+++ b/spindle/engines/microvm/qemu.go
@@ -2,7 +2,9 @@ package microvm
 
 import (
 	"context"
+	"crypto/sha256"
 	_ "embed"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -54,6 +56,8 @@ type QEMUVMHandle struct {
 	serialLogPath string
 	workDir       string
 
+	qmpSocketPath string
+
 	cmd         *exec.Cmd
 	done        chan struct{}
 	qemuLogFile *os.File
@@ -108,6 +112,17 @@ func (qemuRunner) Start(ctx context.Context, cfg VMConfig, volumePaths map[strin
 	}, logger)
 }
 
+// we hash the workDir to get a deterministic qmpSock path
+// since they are AF_UNIX sockets, they are bound by a 108 char long path limit...
+func qmpSocketPath(workDir string) string {
+	base := filepath.Dir(workDir)
+	if workDir == "" {
+		base = os.TempDir()
+	}
+	sum := sha256.Sum256([]byte(workDir))
+	return filepath.Join(base, hex.EncodeToString(sum[:8])+".qmp.sock")
+}
+
 func StartQEMU(ctx context.Context, cfg QEMUConfig, logger *slog.Logger) (VMHandle, error) {
 	if logger == nil {
 		logger = slog.Default()
@@ -163,7 +178,8 @@ func StartQEMU(ctx context.Context, cfg QEMUConfig, logger *slog.Logger) (VMHand
 
 	qmpPath := cfg.QMPPath
 	if qmpPath == "" {
-		qmpPath = filepath.Join(workDir, "qmp.sock")
+		qmpPath = qmpSocketPath(workDir)
+		handle.qmpSocketPath = qmpPath
 	}
 	handle.QMPPath = qmpPath
 
@@ -335,6 +351,12 @@ func (h *QEMUVMHandle) Close() error {
 		closeErr = errors.Join(closeErr, h.cgroup.Close())
 		h.cgroup = nil
 	}
+	if h.qmpSocketPath != "" {
+		if err := os.Remove(h.qmpSocketPath); err != nil && !os.IsNotExist(err) {
+			closeErr = errors.Join(closeErr, err)
+		}
+		h.qmpSocketPath = ""
+	}
 	return closeErr
 }
 
-- 
2.51.2