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    Subject[RFC PATCH V2 1/5] vhost: generalize adding used elem
    Date
    Use one generic vhost_copy_to_user() instead of two dedicated
    accessor. This will simplify the conversion to fine grain
    accessors. About 2% improvement of PPS were seen during vitio-user
    txonly test.

    Signed-off-by: Jason Wang <jasowang@redhat.com>
    ---
    drivers/vhost/vhost.c | 11 +----------
    1 file changed, 1 insertion(+), 10 deletions(-)

    diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
    index a2e5dc7..400aa78 100644
    --- a/drivers/vhost/vhost.c
    +++ b/drivers/vhost/vhost.c
    @@ -2251,16 +2251,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,

    start = vq->last_used_idx & (vq->num - 1);
    used = vq->used->ring + start;
    - if (count == 1) {
    - if (vhost_put_user(vq, heads[0].id, &used->id)) {
    - vq_err(vq, "Failed to write used id");
    - return -EFAULT;
    - }
    - if (vhost_put_user(vq, heads[0].len, &used->len)) {
    - vq_err(vq, "Failed to write used len");
    - return -EFAULT;
    - }
    - } else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
    + if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
    vq_err(vq, "Failed to write used");
    return -EFAULT;
    }
    --
    1.8.3.1
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