[PATCH v2] doc: add PMD known issue

[Zhang, Qi Z]

> -----Original Message-----
> From: Mingjin Ye <mingjinx.ye at intel.com>
> Sent: Saturday, May 6, 2023 6:03 PM
> To: dev at dpdk.org
> Cc: Yang, Qiming <qiming.yang at intel.com>; stable at dpdk.org; Zhou, YidingX
> <yidingx.zhou at intel.com>; Ye, MingjinX <mingjinx.ye at intel.com>; Wu,
> Wenjun1 <wenjun1.wu at intel.com>
> Subject: [PATCH v2] doc: add PMD known issue
> 
> Add a known issue: The ixgbe_vf driver is not multi-process safe.
> 
> Signed-off-by: Mingjin Ye <mingjinx.ye at intel.com>
> ---
> v2: Modify issue description reason.
> ---
>  doc/guides/nics/ixgbe.rst | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/doc/guides/nics/ixgbe.rst b/doc/guides/nics/ixgbe.rst index
> b1d77ab7ab..9fb3c39bf4 100644
> --- a/doc/guides/nics/ixgbe.rst
> +++ b/doc/guides/nics/ixgbe.rst
> @@ -461,3 +461,18 @@ show bypass config
>  Show the bypass configuration for a bypass enabled NIC using the lowest
> port on the NIC::
> 
>     testpmd> show bypass config (port_id)
> +
> +VF driver is not multi-process safe
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Core dump may occur when we start secondary processes on the VF port.
> +Mainstream Linux distributions have the ASLR feature enabled by
> +default, and the text segment of the process memory space is randomized.
> +The secondary process calls the function address shared by the primary
> +process, resulting in a core dump.

Which function did we encounter the issue with? Is this a bug in the PMD? In a multi-process scenario, we should not assume that the addresses of functions are identical across different processes. Additionally, this issue should not be related ASLR because the primary and secondary processes could be two different applications but still share the same DPDK library.

> +
> +   .. Note::
> +
> +          Support for ASLR features varies by distribution. Redhat and
> +          Centos series distributions work fine. Ubuntu distributions
> +          will core dump, other Linux distributions are unknown.
> --
> 2.25.1