patch 'net/i40e: remove incorrect 16B descriptor read block' has been queued to stable release 22.11.5

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 22.11.5

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 03/16/24. 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/bluca/dpdk-stable

This queued commit can be viewed at:
https://github.com/bluca/dpdk-stable/commit/614a3bf8e098e347a3168d928dd6b55bafb76e9b

Thanks.

Luca Boccassi

---
>From 614a3bf8e098e347a3168d928dd6b55bafb76e9b Mon Sep 17 00:00:00 2001
From: Bruce Richardson <bruce.richardson at intel.com>
Date: Tue, 23 Jan 2024 11:40:48 +0000
Subject: [PATCH] net/i40e: remove incorrect 16B descriptor read block

[ upstream commit b527d9585d9cd0446d6bfa39d3a8e896c87883e5 ]

By default, the driver works with 32B descriptors, but has a separate
descriptor read block for reading two descriptors at a time when using
16B descriptors. However, the 32B reads used are not guaranteed to be
atomic, which will cause issues if that is not the case on a system,
since the descriptors may be read in an undefined order.  Remove the
block, to avoid issues, and just use the regular descriptor reading path
for 16B descriptors, if that support is enabled at build time.

Fixes: dafadd73762e ("net/i40e: add AVX2 Rx function")

Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>
---
 drivers/net/i40e/i40e_rxtx_vec_avx2.c | 62 ++++++++++-----------------
 1 file changed, 23 insertions(+), 39 deletions(-)

diff --git a/drivers/net/i40e/i40e_rxtx_vec_avx2.c b/drivers/net/i40e/i40e_rxtx_vec_avx2.c
index 761edb9d20..60baff7970 100644
--- a/drivers/net/i40e/i40e_rxtx_vec_avx2.c
+++ b/drivers/net/i40e/i40e_rxtx_vec_avx2.c
@@ -276,46 +276,30 @@ _recv_raw_pkts_vec_avx2(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 				_mm256_loadu_si256((void *)&sw_ring[i + 4]));
 #endif
 
-		__m256i raw_desc0_1, raw_desc2_3, raw_desc4_5, raw_desc6_7;
-#ifdef RTE_LIBRTE_I40E_16BYTE_RX_DESC
-		/* for AVX we need alignment otherwise loads are not atomic */
-		if (avx_aligned) {
-			/* load in descriptors, 2 at a time, in reverse order */
-			raw_desc6_7 = _mm256_load_si256((void *)(rxdp + 6));
-			rte_compiler_barrier();
-			raw_desc4_5 = _mm256_load_si256((void *)(rxdp + 4));
-			rte_compiler_barrier();
-			raw_desc2_3 = _mm256_load_si256((void *)(rxdp + 2));
-			rte_compiler_barrier();
-			raw_desc0_1 = _mm256_load_si256((void *)(rxdp + 0));
-		} else
-#endif
-		do {
-			const __m128i raw_desc7 = _mm_load_si128((void *)(rxdp + 7));
-			rte_compiler_barrier();
-			const __m128i raw_desc6 = _mm_load_si128((void *)(rxdp + 6));
-			rte_compiler_barrier();
-			const __m128i raw_desc5 = _mm_load_si128((void *)(rxdp + 5));
-			rte_compiler_barrier();
-			const __m128i raw_desc4 = _mm_load_si128((void *)(rxdp + 4));
-			rte_compiler_barrier();
-			const __m128i raw_desc3 = _mm_load_si128((void *)(rxdp + 3));
-			rte_compiler_barrier();
-			const __m128i raw_desc2 = _mm_load_si128((void *)(rxdp + 2));
-			rte_compiler_barrier();
-			const __m128i raw_desc1 = _mm_load_si128((void *)(rxdp + 1));
-			rte_compiler_barrier();
-			const __m128i raw_desc0 = _mm_load_si128((void *)(rxdp + 0));
+		const __m128i raw_desc7 = _mm_load_si128((void *)(rxdp + 7));
+		rte_compiler_barrier();
+		const __m128i raw_desc6 = _mm_load_si128((void *)(rxdp + 6));
+		rte_compiler_barrier();
+		const __m128i raw_desc5 = _mm_load_si128((void *)(rxdp + 5));
+		rte_compiler_barrier();
+		const __m128i raw_desc4 = _mm_load_si128((void *)(rxdp + 4));
+		rte_compiler_barrier();
+		const __m128i raw_desc3 = _mm_load_si128((void *)(rxdp + 3));
+		rte_compiler_barrier();
+		const __m128i raw_desc2 = _mm_load_si128((void *)(rxdp + 2));
+		rte_compiler_barrier();
+		const __m128i raw_desc1 = _mm_load_si128((void *)(rxdp + 1));
+		rte_compiler_barrier();
+		const __m128i raw_desc0 = _mm_load_si128((void *)(rxdp + 0));
 
-			raw_desc6_7 = _mm256_inserti128_si256(
-					_mm256_castsi128_si256(raw_desc6), raw_desc7, 1);
-			raw_desc4_5 = _mm256_inserti128_si256(
-					_mm256_castsi128_si256(raw_desc4), raw_desc5, 1);
-			raw_desc2_3 = _mm256_inserti128_si256(
-					_mm256_castsi128_si256(raw_desc2), raw_desc3, 1);
-			raw_desc0_1 = _mm256_inserti128_si256(
-					_mm256_castsi128_si256(raw_desc0), raw_desc1, 1);
-		} while (0);
+		const __m256i raw_desc6_7 = _mm256_inserti128_si256(
+				_mm256_castsi128_si256(raw_desc6), raw_desc7, 1);
+		const __m256i raw_desc4_5 = _mm256_inserti128_si256(
+				_mm256_castsi128_si256(raw_desc4), raw_desc5, 1);
+		const __m256i raw_desc2_3 = _mm256_inserti128_si256(
+				_mm256_castsi128_si256(raw_desc2), raw_desc3, 1);
+		const __m256i raw_desc0_1 = _mm256_inserti128_si256(
+				_mm256_castsi128_si256(raw_desc0), raw_desc1, 1);
 
 		if (split_packet) {
 			int j;
-- 
2.39.2

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2024-03-14 00:09:21.809495996 +0000
+++ 0023-net-i40e-remove-incorrect-16B-descriptor-read-block.patch	2024-03-14 00:09:20.601614983 +0000
@@ -1 +1 @@
-From b527d9585d9cd0446d6bfa39d3a8e896c87883e5 Mon Sep 17 00:00:00 2001
+From 614a3bf8e098e347a3168d928dd6b55bafb76e9b Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit b527d9585d9cd0446d6bfa39d3a8e896c87883e5 ]
+
@@ -15 +16,0 @@
-Cc: stable at dpdk.org
@@ -24 +25 @@
-index f468c1fd90..19cf0ac718 100644
+index 761edb9d20..60baff7970 100644