Legacy virtio is native endian: if the guest and host endianness differ,
we have to tell vhost so it can swap bytes where appropriate. This is
done through a vhost ring ioctl.
Signed-off-by: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx>
---
hw/virtio/vhost.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 49 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 54851b7..1d7b939 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -17,9 +17,11 @@
#include "hw/hw.h"
#include "qemu/atomic.h"
#include "qemu/range.h"
+#include "qemu/error-report.h"
#include <linux/vhost.h>
#include "exec/address-spaces.h"
#include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/virtio-access.h"
#include "migration/migration.h"
static void vhost_dev_sync_region(struct vhost_dev *dev,
@@ -647,6 +649,27 @@ static void vhost_log_stop(MemoryListener *listener,
/* FIXME: implement */
}
+static int vhost_virtqueue_set_vring_endian_legacy(struct vhost_dev *dev,
+ bool is_big_endian,
+ int vhost_vq_index)
+{
+ struct vhost_vring_state s = {
+ .index = vhost_vq_index,
+ .num = is_big_endian
+ };
+
+ if (!dev->vhost_ops->vhost_call(dev, VHOST_SET_VRING_ENDIAN, &s)) {
+ return 0;
+ }
+
+ if (errno == ENOTTY) {
+ error_report("vhost does not support cross-endian");
+ return -ENOSYS;
+ }
+
+ return -errno;
+}
+
static int vhost_virtqueue_start(struct vhost_dev *dev,
struct VirtIODevice *vdev,
struct vhost_virtqueue *vq,
@@ -677,6 +700,16 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
return -errno;
}
+ if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1) &&
+ virtio_legacy_is_cross_endian(vdev)) {
+ r = vhost_virtqueue_set_vring_endian_legacy(dev,
+ virtio_is_big_endian(vdev),
+ vhost_vq_index);
+ if (r) {
+ return -errno;
+ }
+ }
+
s = l = virtio_queue_get_desc_size(vdev, idx);
a = virtio_queue_get_desc_addr(vdev, idx);
vq->desc = cpu_physical_memory_map(a, &l, 0);
@@ -747,8 +780,9 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
struct vhost_virtqueue *vq,
unsigned idx)
{
+ int vhost_vq_index = idx - dev->vq_index;
struct vhost_vring_state state = {
- .index = idx - dev->vq_index
+ .index = vhost_vq_index,
};
int r;
assert(idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs);
@@ -759,6 +793,20 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
}
virtio_queue_set_last_avail_idx(vdev, idx, state.num);
virtio_queue_invalidate_signalled_used(vdev, idx);
+
+ /* In the cross-endian case, we need to reset the vring endianness to
+ * native as legacy devices expect so by default.
+ */
+ if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1) &&
+ virtio_legacy_is_cross_endian(vdev)) {
+ r = vhost_virtqueue_set_vring_endian_legacy(dev,
+ !virtio_is_big_endian(vdev),
+ vhost_vq_index);
+ if (r < 0) {
+ error_report("failed to reset vring endianness");
+ }
+ }
+
assert (r >= 0);
cpu_physical_memory_unmap(vq->ring, virtio_queue_get_ring_size(vdev, idx),
0, virtio_queue_get_ring_size(vdev, idx));
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