On 07/07/2011 08:57 PM, Michael S. Tsirkin wrote:
> Subject: vhost: used ring logging cleanup
>
> remove extra log bit setting for used ring updates: it's no longer
> necessary. Also, use vhost_avail_event instead of duplicating offset
> math.
>
> Signed-off-by: Michael S. Tsirkin<mst@xxxxxxxxxx>
> ---
>
>> We need set log when updating used flags and avail event. Otherwise guest may
>> see stale values after migration and then do not exit or exit unexpectedly.
>>
>> Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx>
> OK but this means we set the log twice now.
> Also, hardcording offset is not as nice as using
> vhost_avail_event. So I think the below is needed
> on top. Comments?
>
Right, thanks for the cleanup.
> drivers/vhost/vhost.c | 29 +++++++++--------------------
> 1 files changed, 9 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 540591b..c5f96ba 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -946,14 +946,16 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
>
> static int vhost_update_used_flags(struct vhost_virtqueue *vq)
> {
> + void __user *used;
> if (put_user(vq->used_flags,&vq->used->flags)< 0)
> return -EFAULT;
> if (unlikely(vq->log_used)) {
> /* Make sure the flag is seen before log. */
> smp_wmb();
> /* Log used flag write. */
> - log_write(vq->log_base,
> - vq->log_addr + offsetof(struct vring_used, flags),
> + used =&vq->used->flags;
> + log_write(vq->log_base, vq->log_addr +
> + (used - (void __user *)vq->used),
> sizeof vq->used->flags);
> if (vq->log_ctx)
> eventfd_signal(vq->log_ctx, 1);
> @@ -966,13 +968,14 @@ static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
> if (put_user(vq->avail_idx, vhost_avail_event(vq)))
> return -EFAULT;
> if (unlikely(vq->log_used)) {
> + void __user *used;
> /* Make sure the event is seen before log. */
> smp_wmb();
> /* Log avail event write */
> - log_write(vq->log_base,
> - vq->log_addr + offsetof(struct vring_used,
> - ring[vq->num]),
> - sizeof avail_event);
> + used = vhost_avail_event(vq);
> + log_write(vq->log_base, vq->log_addr +
> + (used - (void __user *)vq->used),
> + sizeof *vhost_avail_event(vq));
> if (vq->log_ctx)
> eventfd_signal(vq->log_ctx, 1);
> }
> @@ -1474,20 +1477,6 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
> return false;
> }
> }
> - if (unlikely(vq->log_used)) {
> - void __user *used;
> - /* Make sure data is seen before log. */
> - smp_wmb();
> - used = vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX) ?
> - &vq->used->flags : vhost_avail_event(vq);
> - /* Log used flags or event index entry write. Both are 16 bit
> - * fields. */
> - log_write(vq->log_base, vq->log_addr +
> - (used - (void __user *)vq->used),
> - sizeof(u16));
> - if (vq->log_ctx)
> - eventfd_signal(vq->log_ctx, 1);
> - }
> /* They could have slipped one in as we were doing that: make
> * sure it's written, then check again. */
> smp_mb();
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