On Wed, Jan 13, 2016 at 06:09:47PM +0100, Greg Kurz wrote:
> The way vring endianness is being handled currently obfuscates
> the code in vhost_init_used().
>
> This patch tries to fix that by doing the following:
> - move the the code that adjusts endianness to a dedicated helper
> - export this helper so that backends explicitely call it
>
> No behaviour change.
>
> Signed-off-by: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/vhost/net.c | 3 +++
> drivers/vhost/scsi.c | 3 +++
> drivers/vhost/test.c | 2 ++
> drivers/vhost/vhost.c | 16 +++++++++++-----
> drivers/vhost/vhost.h | 1 +
> 5 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 9eda69e40678..df01c939cd00 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -917,6 +917,9 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>
> vhost_net_disable_vq(n, vq);
> vq->private_data = sock;
> +
> + vhost_adjust_vring_endian(vq);
> +
> r = vhost_init_used(vq);
> if (r)
> goto err_used;
This is in fact a bug in existing code: if vhost_init_used
fails, it preferably should not have side-effects.
It's best to update it last thing.
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 29cfc57d496e..5a8363bfcb74 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -1274,6 +1274,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
> vq = &vs->vqs[i].vq;
> mutex_lock(&vq->mutex);
> vq->private_data = vs_tpg;
> +
> + vhost_adjust_vring_endian(vq);
> +
> vhost_init_used(vq);
> mutex_unlock(&vq->mutex);
> }
> diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> index f2882ac98726..75e3e0e9f5a8 100644
> --- a/drivers/vhost/test.c
> +++ b/drivers/vhost/test.c
> @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test)
> oldpriv = vq->private_data;
> vq->private_data = priv;
>
> + vhost_adjust_vring_endian(vq);
> +
> r = vhost_init_used(&n->vqs[index]);
>
> mutex_unlock(&vq->mutex);
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index e02e06755ab7..b0a00340309e 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -123,6 +123,15 @@ static void vhost_disable_is_le(struct vhost_virtqueue *vq)
> vq->is_le = virtio_legacy_is_little_endian();
> }
>
> +void vhost_adjust_vring_endian(struct vhost_virtqueue *vq)
> +{
> + if (!vq->private_data)
> + vhost_disable_is_le(vq);
> + else
> + vhost_enable_is_le(vq);
> +}
> +EXPORT_SYMBOL_GPL(vhost_adjust_vring_endian);
> +
> static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
> poll_table *pt)
> {
I'd prefer "vhost_update_is_le" here. "endian" might also mean
"user_be". But see below pls.
> @@ -1166,12 +1175,9 @@ int vhost_init_used(struct vhost_virtqueue *vq)
> {
> __virtio16 last_used_idx;
> int r;
> - if (!vq->private_data) {
> - vhost_disable_is_le(vq);
> - return 0;
> - }
>
> - vhost_enable_is_le(vq);
> + if (!vq->private_data)
> + return 0;
>
> r = vhost_update_used_flags(vq);
> if (r)
Looking at how callers use this, maybe we should just rename init_used
to vhost_vq_init_access. The _used suffix was a hint that we
access the vq used ring. But maybe what callers care about is
that it must be called after access_ok.
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index d3f767448a72..88d86f45f756 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
>
> int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> unsigned int log_num, u64 len);
> +void vhost_adjust_vring_endian(struct vhost_virtqueue *vq);
>
> #define vq_err(vq, fmt, ...) do { \
> pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \
--
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