[dpdk-stable] patch 'net/tap: fix build with GCC 11' has been queued to stable release 19.11.9

[Christian Ehrhardt]

Hi,

FYI, your patch has been queued to stable release 19.11.9

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 06/12/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/cpaelzer/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/cpaelzer/dpdk-stable-queue/commit/5ad81654a0397442219b25eac2e9a6a4e099ca7e

Thanks.

Christian Ehrhardt <christian.ehrhardt at canonical.com>

---
>From 5ad81654a0397442219b25eac2e9a6a4e099ca7e Mon Sep 17 00:00:00 2001
From: Ferruh Yigit <ferruh.yigit at intel.com>
Date: Tue, 11 May 2021 14:14:35 +0100
Subject: [PATCH] net/tap: fix build with GCC 11
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

[ upstream commit a625ab89df114bb813a9c8bc3ee3a8f5735bd5fe ]

Reproduced with '--buildtype=debugoptimized' config,
compiler version: gcc (GCC) 12.0.0 20210509 (experimental)

There are multiple build errors, like:
In file included from ../drivers/net/tap/tap_flow.c:13:
In function ‘rte_jhash_2hashes’,
    inlined from ‘rte_jhash’ at ../lib/hash/rte_jhash.h:284:2,
    inlined from ‘tap_flow_set_handle’ at
	../drivers/net/tap/tap_flow.c:1306:12,
    inlined from ‘rss_enable’ at ../drivers/net/tap/tap_flow.c:1909:3,
    inlined from ‘priv_flow_process’ at
	../drivers/net/tap/tap_flow.c:1228:11:
../lib/hash/rte_jhash.h:238:9:
	warning: ‘flow’ may be used uninitialized [-Wmaybe-uninitialized]
  238 |         __rte_jhash_2hashes(key, length, pc, pb, 1);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/net/tap/tap_flow.c: In function ‘priv_flow_process’:
../lib/hash/rte_jhash.h:81:1: note: by argument 1 of type ‘const void *’
	to ‘__rte_jhash_2hashes.constprop’ declared here
 81 | __rte_jhash_2hashes(const void *key, uint32_t length, uint32_t *pc,
    | ^~~~~~~~~~~~~~~~~~~
../drivers/net/tap/tap_flow.c:1028:1: note: ‘flow’ declared here
 1028 | priv_flow_process(struct pmd_internals *pmd,
      | ^~~~~~~~~~~~~~~~~

Fix strict aliasing rule by using union.

Bugzilla ID: 690
Fixes: de96fe68ae95 ("net/tap: add basic flow API patterns and actions")

Signed-off-by: Ferruh Yigit <ferruh.yigit at intel.com>
Acked-by: Kevin Traynor <ktraynor at redhat.com>
---
 drivers/net/tap/tap_flow.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tap/tap_flow.c b/drivers/net/tap/tap_flow.c
index 1538349e9c..2e471832b5 100644
--- a/drivers/net/tap/tap_flow.c
+++ b/drivers/net/tap/tap_flow.c
@@ -1300,10 +1300,16 @@ tap_flow_validate(struct rte_eth_dev *dev,
 static void
 tap_flow_set_handle(struct rte_flow *flow)
 {
+	union {
+		struct rte_flow *flow;
+		const void *key;
+	} tmp;
 	uint32_t handle = 0;
 
+	tmp.flow = flow;
+
 	if (sizeof(flow) > 4)
-		handle = rte_jhash(&flow, sizeof(flow), 1);
+		handle = rte_jhash(tmp.key, sizeof(flow), 1);
 	else
 		handle = (uintptr_t)flow;
 	/* must be at least 1 to avoid letting the kernel choose one for us */
-- 
2.31.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-06-10 14:04:59.361517940 +0200
+++ 0027-net-tap-fix-build-with-GCC-11.patch	2021-06-10 14:04:58.058024583 +0200
@@ -1 +1 @@
-From a625ab89df114bb813a9c8bc3ee3a8f5735bd5fe Mon Sep 17 00:00:00 2001
+From 5ad81654a0397442219b25eac2e9a6a4e099ca7e Mon Sep 17 00:00:00 2001
@@ -8,0 +9,2 @@
+[ upstream commit a625ab89df114bb813a9c8bc3ee3a8f5735bd5fe ]
+
@@ -38 +39,0 @@
-Cc: stable at dpdk.org
@@ -47 +48 @@
-index 1ee6fb30ab..c4f60ce98e 100644
+index 1538349e9c..2e471832b5 100644