[PATCH 20.11] doc: add more instructions for running as non-root

[Xueming(Steven) Li]

> -----Original Message-----
> From: Dmitry Kozlyuk <dkozlyuk at nvidia.com>
> Sent: Monday, August 1, 2022 8:19 PM
> To: stable at dpdk.org
> Cc: Xueming(Steven) Li <xuemingl at nvidia.com>; Bruce Richardson <bruce.richardson at intel.com>
> Subject: [PATCH 20.11] doc: add more instructions for running as non-root
> 
> [ upstream commit 979bb5d493fbbce77eaaf2b4a01ee98f93f76dd9 ]
> 
> The guide to run DPDK applications as non-root in Linux did not provide specific instructions to configure the required access and did not
> explain why each bit is needed.
> The latter is important because running as non-root is one of the ways to tighten security and grant minimal permissions.
> 
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk at nvidia.com>
> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
> ---
> Upstream commit references things missing from 21.11:

Maybe this is the root cause that the patch can't merge, please retry with 20.11:
	https://github.com/steevenlee/dpdk
	Branch: 20.11

> new dpdk-hugepages.py options and memory mapping documentation.
> The script call replaced with a direct mount command.
> Documentation reference is dropped as non-essential.
> 
>  doc/guides/linux_gsg/enable_func.rst | 85 +++++++++++++++++++---------
>  1 file changed, 58 insertions(+), 27 deletions(-)
> 
> diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst
> index 25f87f6b1a..7538d04d97 100644
> --- a/doc/guides/linux_gsg/enable_func.rst
> +++ b/doc/guides/linux_gsg/enable_func.rst
> @@ -66,13 +66,62 @@ The application can then determine what action to take, if any, if the HPET is n  Running DPDK Applications Without
> Root Privileges
>  -------------------------------------------------
> 
> -In order to run DPDK as non-root, the following Linux filesystem objects'
> -permissions should be adjusted to ensure that the Linux account being used to -run the DPDK application has access to them:
> +The following sections describe generic requirements and configuration
> +for running DPDK applications as non-root.
> +There may be additional requirements documented for some drivers.
> 
> -*   All directories which serve as hugepage mount points, for example, ``/dev/hugepages``
> +Hugepages
> +~~~~~~~~~
> 
> -*   If the HPET is to be used,  ``/dev/hpet``
> +Hugepages must be reserved as root before running the application as
> +non-root, for example::
> +
> +  sudo dpdk-hugepages.py --reserve 1G
> +
> +If multi-process is not required, running with ``--in-memory`` bypasses
> +the need to access hugepage mount point and files within it.
> +Otherwise, hugepage directory must be made accessible for writing to
> +the unprivileged user.
> +A good way for managing multiple applications using hugepages is to
> +mount the filesystem with group permissions and add a supplementary
> +group to each application or container.
> +
> +One option is to mount manually::
> +
> +  mount -t hugetlbfs -o pagesize=1G,uid=`id -u`,gid=`id -g` nodev
> + $HOME/huge-1G
> +
> +In production environment, the OS can manage mount points (`systemd
> +example <https://github.com/systemd/systemd/blob/main/units/dev-hugepages.mount>`_).
> +
> +The ``hugetlb`` filesystem has additional options to guarantee or limit
> +the amount of memory that is possible to allocate using the mount point.
> +Refer to the `documentation <https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt>`_.
> +
> +.. note::
> +
> +   Using ``vfio-pci`` kernel driver, if applicable, can eliminate the need
> +   for physical addresses and therefore eliminate the permission requirements
> +   described below.
> +
> +If the driver requires using physical addresses (PA), the executable
> +file must be granted additional capabilities:
> +
> +* ``SYS_ADMIN`` to read ``/proc/self/pagemaps``
> +* ``IPC_LOCK`` to lock hugepages in memory
> +
> +.. code-block:: console
> +
> +   setcap cap_ipc_lock,cap_sys_admin+ep <executable>
> +
> +If physical addresses are not accessible, the following message will
> +appear during EAL initialization::
> +
> +  EAL: rte_mem_virt2phy(): cannot open /proc/self/pagemap: Permission
> + denied
> +
> +It is harmless in case PA are not needed.
> +
> +Resource Limits
> +~~~~~~~~~~~~~~~
> 
>  When running as non-root user, there may be some additional resource limits  that are imposed by the system. Specifically, the following
> resource limits may @@ -87,8 +136,10 @@ need to be adjusted in order to ensure normal DPDK operation:
>  The above limits can usually be adjusted by editing  ``/etc/security/limits.conf`` file, and rebooting.
> 
> -Additionally, depending on which kernel driver is in use, the relevant -resources also should be accessible by the user running the DPDK
> application.
> +Device Control
> +~~~~~~~~~~~~~~
> +
> +If the HPET is to be used, ``/dev/hpet`` permissions must be adjusted.
> 
>  For ``vfio-pci`` kernel driver, the following Linux file system objects'
>  permissions should be adjusted:
> @@ -98,26 +149,6 @@ permissions should be adjusted:
>  * The directories under ``/dev/vfio`` that correspond to IOMMU group numbers of
>    devices intended to be used by DPDK, for example, ``/dev/vfio/50``
> 
> -.. note::
> -
> -    The instructions below will allow running DPDK with ``igb_uio`` or
> -    ``uio_pci_generic`` drivers as non-root with older Linux kernel versions.
> -    However, since version 4.0, the kernel does not allow unprivileged processes
> -    to read the physical address information from the pagemaps file, making it
> -    impossible for those processes to be used by non-privileged users. In such
> -    cases, using the VFIO driver is recommended.
> -
> -For ``igb_uio`` or ``uio_pci_generic`` kernel drivers, the following Linux file -system objects' permissions should be adjusted:
> -
> -*   The userspace-io device files in  ``/dev``, for example,  ``/dev/uio0``, ``/dev/uio1``, and so on
> -
> -*   The userspace-io sysfs config and resource files, for example for ``uio0``::
> -
> -       /sys/class/uio/uio0/device/config
> -       /sys/class/uio/uio0/device/resource*
> -
> -
>  Power Management and Power Saving Functionality
>  -----------------------------------------------
> 
> --
> 2.25.1