[dpdk-dev] [PATCH] doc: update vhost guide

[Mcnamara, John]

> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com]
> Sent: Friday, June 24, 2016 8:53 AM
> To: dev at dpdk.org
> Cc: Xie, Huawei <huawei.xie at intel.com>; Mcnamara, John
> <john.mcnamara at intel.com>; Thomas Monjalon <thomas.monjalon at 6wind.com>;
> Yuanhan Liu <yuanhan.liu at linux.intel.com>
> Subject: [PATCH] doc: update vhost guide
> 
> Mainly on updating vhost-user part: we now support client mode.
> Also refine some words, and add a bit more explanation.
> 
> And made an emphatic statement that you are suggested to use vhost-user
> instead of vhost-cuse, because we have enhanced vhost-user a lot since
> v2.2 (Actually, I doubt there are any people still using vhost-cuse)

Hi Yuahan,

Nice doc and updates. Some minor comments below.


> +
> +* access the guest memory
> +
> +  For QEMU, this is done by using **-object
> + memory-backend-file,share=on,...**
> +  option. Which means QEMU will create a file to serve as the guest RAM.
> +  The **share=on** option allows another process to map that file,
> + which  means it can access the guest RAM.

Fixed width quotes `` `` would be better here than bold ** **.


> +Currently, there are two ways to pass those messages. That results to
> +we have two implementations: vhost-cuse (character devices in user
> +space) and vhost-user. Vhost-cuse creates a user space char dev and
> +hook a function ioctl, so that all ioctl commands (that represent those
> +messages) sent from the frontend (QEMU) will be captured and handled.
> +While vhost-user creates a Unix domain socket file, through which those
> messages are passed.

Probably better to separate the vhost-cuse and vhost-user into 2 paragraphs
to make the text clearer.

Also, it is probably better to standardize on using a hyphen in vhost-cuse
and vhost-user throughout the doc; there are cases with and without.


> +Note that since DPDK v2.2, we have spent a lot of efforts on enhancing
> +vhost-user, such as multiple queue, live migration, reconnect, etc.
> +Thus, **you are encouraged to use vhost-user instead of vhost-cuse**.

In general I prefer to use a simple "Note" in the text, like this, rather
that the RST Note:: directive which creates a more distinctive but usually
unnecessary callout box. However in this case it is probably worth having
this recommendation displayed prominently. Something like the following:

.. Note::

   Since DPDK v2.2, the majority of the development effort has gone into
   enhancing vhost-user, such as multiple queue, live migration, and
   reconnect. Thus, it is strongly advised to use vhost-user instead of
   vhost-cuse.



>   * VHOST_SET_LOG_FD
>   * VHOST_SET_VRING_ERR

Probably best to prefix this list with a sentence that explains what they
are. Something like:

    The supported vhost messages are:

    * ``VHOST_SET_MEM_TABLE``
    * ``VHOST_SET_VRING_KICK``
    * ``VHOST_SET_VRING_CALL``
    * ``VHOST_SET_LOG_FD``
    * ``VHOST_SET_VRING_ERR``

Also, use fixed width quotes here and elsewhere for function or variable
names coming from code.

I will send you on some other suggestions.

John