[PATCH] lib/power: power pmd errata with RTM and gcc-9

[David Hunt <david.hunt@intel.com>]

An errata exists where users may see reduced power savings when using
PMD Power Management. This issue occurs when compiling DPDK applications
with gcc-9 on platforms with TSX enabled. In rte_power_monitor_multi(),
the function may return without successfully starting the RTM
transaction (the _xbegin() fails).

Signed-off-by: David Hunt <david.hunt@intel.com>
---
 doc/guides/rel_notes/release_22_03.rst | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/doc/guides/rel_notes/release_22_03.rst b/doc/guides/rel_notes/release_22_03.rst
index 60e5b4f9aa..34d6f34dba 100644
--- a/doc/guides/rel_notes/release_22_03.rst
+++ b/doc/guides/rel_notes/release_22_03.rst
@@ -313,6 +313,17 @@ Known Issues
    Also, make sure to start the actual text at the margin.
    =======================================================
 
+* **Possible reduced power saving with PMD Power Management.**
+
+  Users may see reduced power savings when using PMD Power Management.
+  This issue occurs when compiling DPDK applications with gcc-9 on
+  platforms with TSX enabled. In rte_power_monitor_multi(), the
+  function may return without successfully starting the RTM
+  transaction (the _xbegin() fails).
+
+  There are three workarounds for this issue. Either build DPDK with gcc-11
+  or newer, build with shared libraries, or build DPDK with fewer drivers.
+
 
 Tested Platforms
 ----------------
-- 
2.17.1