From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id CC83B43E3E; Thu, 11 Apr 2024 08:58:24 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 59E86402A7; Thu, 11 Apr 2024 08:58:24 +0200 (CEST) Received: from dkmailrelay1.smartsharesystems.com (smartserver.smartsharesystems.com [77.243.40.215]) by mails.dpdk.org (Postfix) with ESMTP id 0CC3B40262 for ; Thu, 11 Apr 2024 08:58:23 +0200 (CEST) Received: from smartserver.smartsharesystems.com (smartserver.smartsharesys.local [192.168.4.10]) by dkmailrelay1.smartsharesystems.com (Postfix) with ESMTP id C8F6C209E7; Thu, 11 Apr 2024 08:58:22 +0200 (CEST) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: RE: [PATCH] ethdev: fix strict aliasing lead to link cannot be up Date: Thu, 11 Apr 2024 08:58:19 +0200 X-MimeOLE: Produced By Microsoft Exchange V6.5 Message-ID: <98CBD80474FA8B44BF855DF32C47DC35E9F394@smartserver.smartshare.dk> In-Reply-To: <20240411030749.41874-1-fengchengwen@huawei.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH] ethdev: fix strict aliasing lead to link cannot be up Thread-Index: AdqLvcN3LsNNvUFiSoW3/xIasZ5f0QAHj6Ng References: <20240411030749.41874-1-fengchengwen@huawei.com> From: =?iso-8859-1?Q?Morten_Br=F8rup?= To: "Chengwen Feng" , , Cc: , , , 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 > From: Chengwen Feng [mailto:fengchengwen@huawei.com] > Sent: Thursday, 11 April 2024 05.08 >=20 > Fix a problem introduced by a compiler upgrade (from gcc10 to = gcc12.3), > which will lead the hns3 NIC can't link up. The root cause is strict > aliasing violation in rte_eth_linkstatus_set() with hns3 driver, see > [1] for more details. >=20 > This commit use union to avoid such aliasing violation. >=20 > [1] Strict aliasing problem with rte_eth_linkstatus_set() > https://marc.info/?l=3Ddpdk-dev&m=3D171274148514777&w=3D3 >=20 > Cc: stable@dpdk.org >=20 > Signed-off-by: Chengwen Feng > Signed-off-by: Dengdui Huang > --- The patch mixes atomic and non-atomic access. This is not new for DPDK, which used to rely on compiler built-in = atomics. I'm not sure it needs to be changed, but my suggestion is inline below. I don't think it makes any practical different for 64 bit arch, but it = might for 32 bit arch. > lib/ethdev/ethdev_driver.h | 23 +++++++---------------- > lib/ethdev/rte_ethdev.h | 16 ++++++++++------ > 2 files changed, 17 insertions(+), 22 deletions(-) >=20 > diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h > index 0dbf2dd6a2..9d831d5c84 100644 > --- a/lib/ethdev/ethdev_driver.h > +++ b/lib/ethdev/ethdev_driver.h > @@ -1674,18 +1674,13 @@ static inline int > rte_eth_linkstatus_set(struct rte_eth_dev *dev, > const struct rte_eth_link *new_link) > { > - RTE_ATOMIC(uint64_t) *dev_link =3D (uint64_t __rte_atomic *)&(dev- > >data->dev_link); > - union { > - uint64_t val64; > - struct rte_eth_link link; > - } orig; > - > - RTE_BUILD_BUG_ON(sizeof(*new_link) !=3D sizeof(uint64_t)); > + struct rte_eth_link old_link; >=20 > - orig.val64 =3D rte_atomic_exchange_explicit(dev_link, *(const > uint64_t *)new_link, > - rte_memory_order_seq_cst); > + old_link.val64 =3D rte_atomic_exchange_explicit(&dev->data- > >dev_link.val64, old_link.val64 should be written using: rte_atomic_store_explicit(&old_link.val64, ..., = rte_memory_order_seq_cst) > + new_link->val64, new_link->val64 should be read using: rte_atomic_load_explicit(&new_link->val64, rte_memory_order_seq_cst) > + rte_memory_order_seq_cst); >=20 > - return (orig.link.link_status =3D=3D new_link->link_status) ? -1 : = 0; > + return (old_link.link_status =3D=3D new_link->link_status) ? -1 : 0; > } >=20 > /** > @@ -1701,12 +1696,8 @@ static inline void > rte_eth_linkstatus_get(const struct rte_eth_dev *dev, > struct rte_eth_link *link) > { > - RTE_ATOMIC(uint64_t) *src =3D (uint64_t __rte_atomic *)&(dev->data- > >dev_link); > - uint64_t *dst =3D (uint64_t *)link; > - > - RTE_BUILD_BUG_ON(sizeof(*link) !=3D sizeof(uint64_t)); > - > - *dst =3D rte_atomic_load_explicit(src, rte_memory_order_seq_cst); > + link->val64 =3D rte_atomic_load_explicit(&dev->data->dev_link.val64, link->val64 should be written using: rte_atomic_store_explicit(&link->val64, ..., rte_memory_order_seq_cst) > + rte_memory_order_seq_cst); > } >=20 > /** > diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h > index 147257d6a2..0b5d3d2318 100644 > --- a/lib/ethdev/rte_ethdev.h > +++ b/lib/ethdev/rte_ethdev.h > @@ -332,12 +332,16 @@ struct rte_eth_stats { > /** > * A structure used to retrieve link-level information of an Ethernet > port. > */ > -__extension__ > -struct __rte_aligned(8) rte_eth_link { /**< aligned for atomic64 > read/write */ > - uint32_t link_speed; /**< RTE_ETH_SPEED_NUM_ */ > - uint16_t link_duplex : 1; /**< RTE_ETH_LINK_[HALF/FULL]_DUPLEX > */ > - uint16_t link_autoneg : 1; /**< RTE_ETH_LINK_[AUTONEG/FIXED] */ > - uint16_t link_status : 1; /**< RTE_ETH_LINK_[DOWN/UP] */ > +struct rte_eth_link { > + union { > + uint64_t val64; /**< used for atomic64 read/write */ The type of val64 should be: RTE_ATOMIC(uint64_t) > + struct { > + uint32_t link_speed; /**< RTE_ETH_SPEED_NUM_ > */ > + uint16_t link_duplex : 1; /**< > RTE_ETH_LINK_[HALF/FULL]_DUPLEX */ > + uint16_t link_autoneg : 1; /**< > RTE_ETH_LINK_[AUTONEG/FIXED] */ > + uint16_t link_status : 1; /**< > RTE_ETH_LINK_[DOWN/UP] */ > + }; > + }; > }; >=20 > /**@{@name Link negotiation > -- > 2.17.1