1 files changed, 9 insertions, 0 deletions
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 7bb994bbf2..741d222c3f 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1353,6 +1353,15 @@ static void coroutine_fn v9fs_version(void *opaque)
         goto out;
     }
 
+    /* 8192 is the default msize of Linux clients */
+    if (s->msize <= 8192 && !(s->ctx.export_flags & V9FS_NO_PERF_WARN)) {
+        warn_report_once(
+            "9p: degraded performance: a reasonable high msize should be "
+            "chosen on client/guest side (chosen msize is <= 8192). See "
+            "https://wiki.qemu.org/Documentation/9psetup#msize for details."
+        );
+    }
+
 marshal:
     err = pdu_marshal(pdu, offset, "ds", s->msize, &version);
     if (err < 0) {