virtio-9p: fix any_layout

virtio pci allows any device to have a modern interface,
this in turn requires ANY_LAYOUT support.
Fix up ANY_LAYOUT for virtio-9p.

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index 6ef8af3..f972731 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -14,6 +14,7 @@
 #include "hw/virtio/virtio.h"
 #include "hw/i386/pc.h"
 #include "qemu/error-report.h"
+#include "qemu/iov.h"
 #include "qemu/sockets.h"
 #include "virtio-9p.h"
 #include "fsdev/qemu-fsdev.h"
@@ -3261,16 +3262,26 @@ void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
 
     while ((pdu = alloc_pdu(s)) &&
             (len = virtqueue_pop(vq, &pdu->elem)) != 0) {
-        uint8_t *ptr;
+        struct {
+            uint32_t size_le;
+            uint8_t id;
+            uint16_t tag_le;
+        } QEMU_PACKED out;
+        int len;
+
         pdu->s = s;
         BUG_ON(pdu->elem.out_num == 0 || pdu->elem.in_num == 0);
-        BUG_ON(pdu->elem.out_sg[0].iov_len < 7);
+        QEMU_BUILD_BUG_ON(sizeof out != 7);
+
+        len = iov_to_buf(pdu->elem.out_sg, pdu->elem.out_num, 0,
+                         &out, sizeof out);
+        BUG_ON(len != sizeof out);
+
+        pdu->size = le32_to_cpu(out.size_le);
 
-        ptr = pdu->elem.out_sg[0].iov_base;
+        pdu->id = out.id;
+        pdu->tag = le16_to_cpu(out.tag_le);
 
-        pdu->size = le32_to_cpu(*(uint32_t *)ptr);
-        pdu->id = ptr[4];
-        pdu->tag = le16_to_cpu(*(uint16_t *)(ptr + 5));
         qemu_co_queue_init(&pdu->complete);
         submit_pdu(s, pdu);
     }