[Qemu-devel] [PATCH] Peek dont read for vmdescription

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The VMDescription section maybe after the EOF mark, the current code
does a 'qemu_get_byte' and either gets the header byte identifying the
description or an error (which it ignores).  Doing the 'get' upsets
RDMA which hangs on old machine types without the VMDescription.

Using 'qemu_peek_byte' avoids that.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/savevm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 2004dce..4bd3709 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1128,9 +1128,14 @@ int qemu_loadvm_state(QEMUFile *f)
      * Try to read in the VMDESC section as well, so that dumping tools that
      * intercept our migration stream have the chance to see it.
      */
-    if (qemu_get_byte(f) == QEMU_VM_VMDESCRIPTION) {
-        uint32_t size = qemu_get_be32(f);
+    if (qemu_peek_byte(f, 0) == QEMU_VM_VMDESCRIPTION) {
         uint8_t *buf = g_malloc(0x1000);
+        uint32_t size;
+
+        /* Consume the peeked byte */
+        size = qemu_get_byte(f);
+
+        size = qemu_get_be32(f);
 
         while (size > 0) {
             uint32_t read_chunk = MIN(size, 0x1000);
-- 
2.4.3