doc: clarify restrictions to run as non-root

Since modern kernels don't allow unprivileged processes to read the
pagemaps file, the instructions on running as non-root are out-of-date. Add
a note clarifying that they will only work with earlier kernel versions.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>

diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst
index e6c806b..5ac0184 100644 (file)
--- a/doc/guides/linux_gsg/enable_func.rst
+++ b/doc/guides/linux_gsg/enable_func.rst
@@ -87,6 +87,14 @@ The application can then determine what action to take, if any, if the HPET is n
 Running DPDK Applications Without Root Privileges
 --------------------------------------------------------
 
 Running DPDK Applications Without Root Privileges
 --------------------------------------------------------
 

+.. note::
+
+    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
+

 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
 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