[dpdk-stable] [PATCH v2 1/2] doc/linux_gsg: clarify instructions on running as non-root

[Anatoly Burakov <anatoly.burakov@intel.com>]

The current instructions are slightly out of date when it comes to
providing information about setting up the system for using DPDK as
non-root, so update them.

Cc: stable@dpdk.org

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
---

Notes:
    v2:
    - Moved VFIO description to be first

 doc/guides/linux_gsg/enable_func.rst | 54 ++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 15 deletions(-)

diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst
index b2bda80bb7..a000def6cc 100644
--- a/doc/guides/linux_gsg/enable_func.rst
+++ b/doc/guides/linux_gsg/enable_func.rst
@@ -58,22 +58,42 @@ The application can then determine what action to take, if any, if the HPET is n
     if any, and on what is available on the system at runtime.
 
 Running DPDK Applications Without Root Privileges
---------------------------------------------------------
+-------------------------------------------------
 
-.. note::
+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 instructions below will allow running DPDK 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 use HW
-    devices which require physical addresses
+*   All directories which serve as hugepage mount points, for example, ``/dev/hugepages``
 
-Although applications using the DPDK use network ports and other hardware resources directly,
-with a number of small permission adjustments it is possible to run these applications as a user other than "root".
-To do so, the ownership, or permissions, on the following Linux file system objects should be adjusted to ensure that
-the Linux user account being used to run the DPDK application has access to them:
+*   If the HPET is to be used,  ``/dev/hpet``
 
-*   All directories which serve as hugepage mount points, for example,   ``/mnt/huge``
+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
+need to be adjusted in order to ensure normal DPDK operation:
+
+* RLIMIT_LOCKS (number of file locks that can be held by a process)
+
+* RLIMIT_NOFILE (number of open file descriptors that can be held open by a process)
+
+* RLIMIT_MEMLOCK (amount of pinned pages the process is allowed to have)
+
+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.
+
+For ``vfio-pci`` kernel driver, the following Linux file system objects'
+permissions should be adjusted:
+
+* The VFIO device file, ``/dev/vfio/vfio``
+
+* The directories under ``/dev/vfio`` that correspond to IOMMU group numbers of
+  devices intended to be used by DPDK, for example, ``/dev/vfio/50``
+
+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
 
@@ -82,11 +102,15 @@ the Linux user account being used to run the DPDK application has access to them
        /sys/class/uio/uio0/device/config
        /sys/class/uio/uio0/device/resource*
 
-*   If the HPET is to be used,  ``/dev/hpet``
-
 .. note::
 
-    On some Linux installations, ``/dev/hugepages``  is also a hugepage mount point created by default.
+    The instructions above will allow running DPDK with ``igb_uio`` driver 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.
+
 
 Power Management and Power Saving Functionality
 -----------------------------------------------
-- 
2.17.1