Commit 032a74a1c0fcdd5fd1c69e56126b4c857ee36611
("virtio-net: byteswap virtio-net header") breaks any layout by
requiring out_sg[0].iov_len >= n->guest_hdr_len. Fixing this by
copying header to temporary buffer if swap is needed, and then use
this buffer as part of out_sg.
Fixes 032a74a1c0fcdd5fd1c69e56126b4c857ee36611
("virtio-net: byteswap virtio-net header")
Cc: qemu-sta...@nongnu.org
Cc: c...@fr.ibm.com
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
Changes from V1:
- avoid header copying if there's no need to do header swap
- don't write the header back
---
hw/net/virtio-net.c | 17 ++++++++++++++---
include/hw/virtio/virtio-access.h | 9 +++++++++
2 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index e3c2db3..12322bd 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1142,7 +1142,8 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
ssize_t ret, len;
unsigned int out_num = elem.out_num;
struct iovec *out_sg = &elem.out_sg[0];
- struct iovec sg[VIRTQUEUE_MAX_SIZE];
+ struct iovec sg[VIRTQUEUE_MAX_SIZE], sg2[VIRTQUEUE_MAX_SIZE];
+ struct virtio_net_hdr hdr;
if (out_num < 1) {
error_report("virtio-net header not in first element");
@@ -1150,11 +1151,21 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
}
if (n->has_vnet_hdr) {
- if (out_sg[0].iov_len < n->guest_hdr_len) {
+ if (iov_size(out_sg, out_num) < n->guest_hdr_len) {
error_report("virtio-net header incorrect");
exit(1);
}
- virtio_net_hdr_swap(vdev, (void *) out_sg[0].iov_base);
+ if (virtio_needs_swap(vdev)) {
+ iov_to_buf(out_sg, out_num, 0, &hdr, sizeof(hdr));
+ virtio_net_hdr_swap(vdev, (void *) &hdr);
+ sg2[0].iov_base = &hdr;
+ sg2[0].iov_len = sizeof(hdr);
+ out_num = iov_copy(&sg2[1], ARRAY_SIZE(sg2) - 1,
+ out_sg, out_num,
+ sizeof(hdr), -1);
+ out_num += 1;
+ out_sg = sg2;
+ }
}
/*
diff --git a/include/hw/virtio/virtio-access.h
b/include/hw/virtio/virtio-access.h
index cee5dd7..1ec1dfd 100644
--- a/include/hw/virtio/virtio-access.h
+++ b/include/hw/virtio/virtio-access.h
@@ -143,6 +143,15 @@ static inline uint64_t virtio_ldq_p(VirtIODevice *vdev,
const void *ptr)
}
}
+static inline bool virtio_needs_swap(VirtIODevice *vdev)
+{
+#ifdef HOST_WORDS_BIGENDIAN
+ return virtio_access_is_big_endian(vdev) ? false : true;
+#else
+ return virtio_access_is_big_endian(vdev) ? true : false;
+#endif
+}
+
static inline uint16_t virtio_tswap16(VirtIODevice *vdev, uint16_t s)
{
#ifdef HOST_WORDS_BIGENDIAN
--
2.1.4
