From ad9cb0ba58a57c7a75a672cdf845f64c4a97adc6 Mon Sep 17 00:00:00 2001
From: Greg Kurz <groug@kaod.org>
Date: Wed, 23 Nov 2022 14:22:28 +0100
Subject: [PATCH] govmm: Optionally pass QMP listener to QEMU

QEMU's -qmp option can be passed the file descriptor of a socket that
is already in listening mode. This is done with by passing `fd=XXX`
to `-qmp` instead of a path. Note that these two options are mutually
exclusive : QEMU errors out if both are passed, so we check that as
well in the validation function.

While here add the `path=` stanza in the path based case for clarity.

Signed-off-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit 8a4f08cb0f7c5471cb4fe274eca0d79ba8539c27)
Signed-off-by: Greg Kurz <groug@kaod.org>
---
 src/runtime/pkg/govmm/qemu/qemu.go      | 14 +++++++++++--
 src/runtime/pkg/govmm/qemu/qemu_test.go | 26 ++++++++++++++++++++++---
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/src/runtime/pkg/govmm/qemu/qemu.go b/src/runtime/pkg/govmm/qemu/qemu.go
index 4b36df2ea3..b47a8fb175 100644
--- a/src/runtime/pkg/govmm/qemu/qemu.go
+++ b/src/runtime/pkg/govmm/qemu/qemu.go
@@ -2327,6 +2327,9 @@ type QMPSocket struct {
 	// Type is the socket type (e.g. "unix").
 	Type QMPSocketType
 
+	// QMP listener file descriptor to be passed to qemu
+	FD *os.File
+
 	// Name is the socket name.
 	Name string
 
@@ -2339,7 +2342,8 @@ type QMPSocket struct {
 
 // Valid returns true if the QMPSocket structure is valid and complete.
 func (qmp QMPSocket) Valid() bool {
-	if qmp.Type == "" || qmp.Name == "" {
+	// Exactly one of Name of FD must be set.
+	if qmp.Type == "" || (qmp.Name == "") == (qmp.FD == nil) {
 		return false
 	}
 
@@ -2679,7 +2683,13 @@ func (config *Config) appendQMPSockets() {
 			continue
 		}
 
-		qmpParams := append([]string{}, fmt.Sprintf("%s:%s", q.Type, q.Name))
+		var qmpParams []string
+		if q.FD != nil {
+			qemuFDs := config.appendFDs([]*os.File{q.FD})
+			qmpParams = append([]string{}, fmt.Sprintf("%s:fd=%d", q.Type, qemuFDs[0]))
+		} else {
+			qmpParams = append([]string{}, fmt.Sprintf("%s:path=%s", q.Type, q.Name))
+		}
 		if q.Server {
 			qmpParams = append(qmpParams, "server=on")
 			if q.NoWait {
diff --git a/src/runtime/pkg/govmm/qemu/qemu_test.go b/src/runtime/pkg/govmm/qemu/qemu_test.go
index 501c07fdf1..563a9f7fb1 100644
--- a/src/runtime/pkg/govmm/qemu/qemu_test.go
+++ b/src/runtime/pkg/govmm/qemu/qemu_test.go
@@ -698,8 +698,8 @@ func TestFailToAppendCPUs(t *testing.T) {
 	}
 }
 
-var qmpSingleSocketServerString = "-qmp unix:cc-qmp,server=on,wait=off"
-var qmpSingleSocketString = "-qmp unix:cc-qmp"
+var qmpSingleSocketServerString = "-qmp unix:path=cc-qmp,server=on,wait=off"
+var qmpSingleSocketString = "-qmp unix:path=cc-qmp"
 
 func TestAppendSingleQMPSocketServer(t *testing.T) {
 	qmp := QMPSocket{
@@ -722,7 +722,27 @@ func TestAppendSingleQMPSocket(t *testing.T) {
 	testAppend(qmp, qmpSingleSocketString, t)
 }
 
-var qmpSocketServerString = "-qmp unix:cc-qmp-1,server=on,wait=off -qmp unix:cc-qmp-2,server=on,wait=off"
+var qmpSocketServerFdString = "-qmp unix:fd=3,server=on,wait=off"
+
+func TestAppendQMPSocketServerFd(t *testing.T) {
+	foo, _ := os.CreateTemp(os.TempDir(), "govmm-qemu-test")
+
+	defer func() {
+		_ = foo.Close()
+		_ = os.Remove(foo.Name())
+	}()
+
+	qmp := QMPSocket{
+		Type:   "unix",
+		FD:     foo,
+		Server: true,
+		NoWait: true,
+	}
+
+	testAppend(qmp, qmpSocketServerFdString, t)
+}
+
+var qmpSocketServerString = "-qmp unix:path=cc-qmp-1,server=on,wait=off -qmp unix:path=cc-qmp-2,server=on,wait=off"
 
 func TestAppendQMPSocketServer(t *testing.T) {
 	qmp := []QMPSocket{