Commit 04b7a152 authored by Greg Kurz's avatar Greg Kurz Committed by Michael S. Tsirkin
Browse files

vhost: set vring endianness for legacy virtio 



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: default avatarGreg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 41d283bd

hw/virtio/vhost.c

+49 −1
Original line number Diff line number Diff line
@@ -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 struct vhost_log *vhost_log;
@@ -686,6 +688,27 @@ 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,
@@ -716,6 +739,16 @@ 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);
@@ -786,8 +819,9 @@ 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);
@@ -798,6 +832,20 @@ 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));