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Mon, 11 Jul 2022 14:14:22 +0200 (CEST) From: =?UTF-8?q?Mattias=20R=C3=B6nnblom?= To: CC: Emil Berg , , , , , , , =?UTF-8?q?Morten=20Br=C3=B8rup?= , =?UTF-8?q?Mattias=20R=C3=B6nnblom?= Subject: [PATCH v3 2/2] net: have checksum routines accept unaligned data Date: Mon, 11 Jul 2022 14:11:32 +0200 Message-ID: <20220711121132.34546-2-mattias.ronnblom@ericsson.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220711121132.34546-1-mattias.ronnblom@ericsson.com> References: <20220711121132.34546-1-mattias.ronnblom@ericsson.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: cdceaf5c-20fc-41b2-2afe-08da6336e43c X-MS-TrafficTypeDiagnostic: DB9PR07MB7210:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:192.176.1.74; CTRY:SE; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:oa.msg.ericsson.com; PTR:office365.se.ericsson.net; CAT:NONE; SFS:(13230016)(4636009)(39860400002)(396003)(376002)(136003)(346002)(40470700004)(36840700001)(46966006)(83380400001)(8676002)(6916009)(478600001)(40460700003)(36860700001)(40480700001)(82960400001)(5660300002)(2906002)(4326008)(41300700001)(6666004)(356005)(8936002)(70586007)(82740400003)(26005)(70206006)(6266002)(66574015)(107886003)(47076005)(2616005)(1076003)(316002)(186003)(86362001)(82310400005)(336012)(54906003)(36756003)(7636003); DIR:OUT; SFP:1101; X-OriginatorOrg: ericsson.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jul 2022 12:14:23.4253 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: cdceaf5c-20fc-41b2-2afe-08da6336e43c X-MS-Exchange-CrossTenant-Id: 92e84ceb-fbfd-47ab-be52-080c6b87953f X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=92e84ceb-fbfd-47ab-be52-080c6b87953f; Ip=[192.176.1.74]; Helo=[oa.msg.ericsson.com] X-MS-Exchange-CrossTenant-AuthSource: VE1EUR02FT008.eop-EUR02.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB9PR07MB7210 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org __rte_raw_cksum() (used by rte_raw_cksum() among others) accessed its data through an uint16_t pointer, which allowed the compiler to assume the data was 16-bit aligned. This in turn would, with certain architectures and compiler flag combinations, result in code with SIMD load or store instructions with restrictions on data alignment. This patch keeps the old algorithm, but data is read using memcpy() instead of direct pointer access, forcing the compiler to always generate code that handles unaligned input. The __may_alias__ GCC attribute is no longer needed. The data on which the Internet checksum functions operates are almost always 16-bit aligned, but there are exceptions. In particular, the PDCP protocol header may (literally) have an odd size. Performance impact seems to range from none to a very slight regression. Bugzilla ID: 1035 Cc: stable@dpdk.org --- v3: * Use RTE_ALIGN_FLOOR() in the pointer arithmetic (Olivier Matz). v2: * Simplified the odd-length conditional (Morten Brørup). Reviewed-by: Morten Brørup Signed-off-by: Mattias Rönnblom --- lib/net/rte_ip.h | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/lib/net/rte_ip.h b/lib/net/rte_ip.h index b502481670..ecd250e9be 100644 --- a/lib/net/rte_ip.h +++ b/lib/net/rte_ip.h @@ -160,18 +160,21 @@ rte_ipv4_hdr_len(const struct rte_ipv4_hdr *ipv4_hdr) static inline uint32_t __rte_raw_cksum(const void *buf, size_t len, uint32_t sum) { - /* extend strict-aliasing rules */ - typedef uint16_t __attribute__((__may_alias__)) u16_p; - const u16_p *u16_buf = (const u16_p *)buf; - const u16_p *end = u16_buf + len / sizeof(*u16_buf); + const void *end; - for (; u16_buf != end; ++u16_buf) - sum += *u16_buf; + for (end = RTE_PTR_ADD(buf, RTE_ALIGN_FLOOR(len, sizeof(uint16_t))); + buf != end; buf = RTE_PTR_ADD(buf, sizeof(uint16_t))) { + uint16_t v; + + memcpy(&v, buf, sizeof(uint16_t)); + sum += v; + } /* if length is odd, keeping it byte order independent */ if (unlikely(len % 2)) { uint16_t left = 0; - *(unsigned char *)&left = *(const unsigned char *)end; + + memcpy(&left, end, 1); sum += left; } -- 2.25.1