vfio-user: add 'x-msg-timeout' option

By default, the vfio-user subsystem will wait 5 seconds for a message
reply from the server. Add an option to allow this to be configurable.

Originally-by: John Johnson <john.g.johnson@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250625193012.2316242-16-john.levon@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

3 files changed, 10 insertions, 3 deletions

diff --git a/hw/vfio-user/pci.c b/hw/vfio-user/pci.c
index 040660d..f260bea 100644
--- a/hw/vfio-user/pci.c
+++ b/hw/vfio-user/pci.c
@@ -23,6 +23,7 @@ struct VFIOUserPCIDevice {
     VFIOPCIDevice device;
     SocketAddress *socket;
     bool send_queued;   /* all sends are queued */
+    uint32_t wait_time; /* timeout for message replies */
 };
 
 /*
@@ -267,6 +268,9 @@ static void vfio_user_pci_realize(PCIDevice *pdev, Error **errp)
         proxy->flags |= VFIO_PROXY_FORCE_QUEUED;
     }
 
+    /* user specified or 5 sec default */
+    proxy->wait_time = udev->wait_time;
+
     if (!vfio_user_validate_version(proxy, errp)) {
         goto error;
     }
@@ -398,6 +402,7 @@ static const Property vfio_user_pci_dev_properties[] = {
     DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
                        sub_device_id, PCI_ANY_ID),
     DEFINE_PROP_BOOL("x-send-queued", VFIOUserPCIDevice, send_queued, false),
+    DEFINE_PROP_UINT32("x-msg-timeout", VFIOUserPCIDevice, wait_time, 5000),
 };
 
 static void vfio_user_pci_set_socket(Object *obj, Visitor *v, const char *name,
diff --git a/hw/vfio-user/proxy.c b/hw/vfio-user/proxy.c
index cb93d9a..c3724ba 100644
--- a/hw/vfio-user/proxy.c
+++ b/hw/vfio-user/proxy.c
@@ -21,7 +21,6 @@
 #include "qemu/main-loop.h"
 #include "system/iothread.h"
 
-static int wait_time = 5000;   /* wait up to 5 sec for busy servers */
 static IOThread *vfio_user_iothread;
 
 static void vfio_user_shutdown(VFIOUserProxy *proxy);
@@ -686,7 +685,8 @@ bool vfio_user_send_wait(VFIOUserProxy *proxy, VFIOUserHdr *hdr,
 
     if (ok) {
         while (!msg->complete) {
-            if (!qemu_cond_timedwait(&msg->cv, &proxy->lock, wait_time)) {
+            if (!qemu_cond_timedwait(&msg->cv, &proxy->lock,
+                                     proxy->wait_time)) {
                 VFIOUserMsgQ *list;
 
                 list = msg->pending ? &proxy->pending : &proxy->outgoing;
@@ -758,7 +758,8 @@ void vfio_user_wait_reqs(VFIOUserProxy *proxy)
         msg->type = VFIO_MSG_WAIT;
         proxy->last_nowait = NULL;
         while (!msg->complete) {
-            if (!qemu_cond_timedwait(&msg->cv, &proxy->lock, wait_time)) {
+            if (!qemu_cond_timedwait(&msg->cv, &proxy->lock,
+                                     proxy->wait_time)) {
                 VFIOUserMsgQ *list;
 
                 list = msg->pending ? &proxy->pending : &proxy->outgoing;
diff --git a/hw/vfio-user/proxy.h b/hw/vfio-user/proxy.h
index 39092c0..6b29cd7 100644
--- a/hw/vfio-user/proxy.h
+++ b/hw/vfio-user/proxy.h
@@ -67,6 +67,7 @@ typedef struct VFIOUserProxy {
     uint64_t max_bitmap;
     uint64_t migr_pgsize;
     int flags;
+    uint32_t wait_time;
     QemuCond close_cv;
     AioContext *ctx;
     QEMUBH *req_bh;