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Fri, 7 Mar 2025 10:17:18 +0000 Date: Fri, 7 Mar 2025 11:17:11 +0100 From: Maciej Fijalkowski To: Alexander Lobakin CC: , Michal Kubiak , Tony Nguyen , "Przemek Kitszel" , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Alexei Starovoitov" , Daniel Borkmann , "Jesper Dangaard Brouer" , John Fastabend , Simon Horman , , , Subject: Re: [PATCH net-next 05/16] idpf: fix Rx descriptor ready check barrier in splitq Message-ID: References: <20250305162132.1106080-1-aleksander.lobakin@intel.com> <20250305162132.1106080-6-aleksander.lobakin@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250305162132.1106080-6-aleksander.lobakin@intel.com> X-ClientProxiedBy: VI1PR02CA0060.eurprd02.prod.outlook.com (2603:10a6:802:14::31) To DM4PR11MB6117.namprd11.prod.outlook.com (2603:10b6:8:b3::19) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR11MB6117:EE_|CY5PR11MB6163:EE_ X-MS-Office365-Filtering-Correlation-Id: f2e208ae-11b5-4979-5d54-08dd5d613dd7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?dolS2nS9cE8JHLxPgJKL00lrce8lmrtLosJDSNXhJgwtUGDnvmk7Yy39+vg7?= =?us-ascii?Q?bEb2Sfi6cMcdGl9pNBiAkXr1BjPRYMbFXcPhi1CnRE7K56DWLGUc0Mbly9Dq?= =?us-ascii?Q?63bdnUWR1j7kEC9vmv/XB1QEpeaNnxwbrEDp7RWzlsr5QRzY3cyJi7muzV7w?= =?us-ascii?Q?3cChUlcGzqeF3bZB7+3mn9oqwimX3k2l19RbouXVX9pl5lcvLwFeugJ9nAVM?= =?us-ascii?Q?Xd5JxOHuC66bgHWSz2xmFfqyJ/8WR1jO+gilcccNDYwUsLY2OGjWLjxBmcyn?= =?us-ascii?Q?VGFgt9VE7AhusH/5oEO7IRShs/eZv6hKWuxI+qhJVj3dQEZYL9dJmQ4YjogQ?= =?us-ascii?Q?ht7iicX4wv1CxrXNxFNli3zPtP1/mWkXMWdZa0nT16GRDWuEMBv+mzZr7Wyu?= =?us-ascii?Q?p4FXGzQ0l9Mr6rC9vYEEZXM/9pFL3/UvaPnAEjYkuFPRb+ZDPsyKDcqIcM/p?= =?us-ascii?Q?4obWXA6H7rDuvApP9iE5tCNZxI445oTObweWW71b6VDgXq20pYEb1Uf4BAnw?= =?us-ascii?Q?80HFsGmd3+5ER6FMyQe2zt+o8gj4/UmVWW6R/2p/QBzzRL67R9Sm1CX2d4mn?= =?us-ascii?Q?9JTp+qxbY8aUmAHfC32DDtOkWJkMG/LGOq5bLdd9s9KF8iCPkFMSqw/DW8Lv?= =?us-ascii?Q?rRBwBXmvSDja3Xk87IT2JoxgC9taDqjvNUp1mnLLECbhGcoNoH2cc/d0S1K2?= =?us-ascii?Q?UISPkhCDp0Q/UdiswI11qGuEpKgtChPWswjd9ajJa+0XEwGXTaxli/cpF4vd?= =?us-ascii?Q?nKwijOl0hWx3HATozeAfg8iBF78JFr0v3CldZtftSsW5yOesysd6RQX8FD/G?= =?us-ascii?Q?caeJQ0LNVYLEsYiux9wiwRaVZW1cly99drRzFYxHaSWr2r7tYPW1f+v2H4Qw?= =?us-ascii?Q?vHJevqzfOn3w4Z4vrrT9bAIIGfcuz+IlvU3HNZ8z54Klwn9fQi4mdKzJUEbM?= =?us-ascii?Q?lzx7RONI1hDhj0j+5XG6kLRhAe6H/TX5nehm5BLYvmboq6AWWetGGBlSMlr8?= =?us-ascii?Q?eitI1zxXDHYxTYKlrvuCjzHCJBuj4FhbMD4+QFL782O+I4ffn8LxCbvheofG?= =?us-ascii?Q?34JjUy5oCWQYOSih3h0pDFECpNZJgqhJ/b76Qu+a6oWiAj2yQe+K8Km+KKPV?= =?us-ascii?Q?DpBcPBIm1bQaNsU4+BAY1YLdo/g74w0jbpQybd4VslW4rvuvtCkZkEBEqI4E?= =?us-ascii?Q?e+dfZwthhnMLUre+zWhwVx5CkSLgYOPC7tnqvrcrm9qnPWa5sKPwqOF8R2kE?= =?us-ascii?Q?Ml97Lj01f6kcm7D6qWDyhCle8zyKjOZNI+AGqciiCqpIG4opjQGHGTyigaFC?= =?us-ascii?Q?ACqIutdCjoxeUtfsCI0wkWiNS4sRGh3B4B+qElQfKG8gRpK3oaRSqCn3o53z?= =?us-ascii?Q?Z1kwb3iTc8LPj9oxdvdGZSZIjNkJFUELpXTuq830qVFoDTHQQ6OWpLVY6p3T?= =?us-ascii?Q?SrnaAZ95wVreZXiHBpFHijgz6JVe1luepWfbHbHqinwTl8sDOrzSIJUuU4sq?= =?us-ascii?Q?aMAGgY44olsZxIgFH39J92aGJi3/YI7b8FqdsfPp6tlkbcNUGcVSt9IICvo6?= =?us-ascii?Q?a2V97XjR74g274qBUXt7DnKtSLDCN5njjj/GF8X2jkpChoMC4J01Zp1sX2LV?= =?us-ascii?Q?QA=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: f2e208ae-11b5-4979-5d54-08dd5d613dd7 X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB6117.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Mar 2025 10:17:18.8355 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: SjOBGwLigk1qiiE/OPwRfWUUVZC50v7uKYsDfRXmWVd9oXBqLU7lMJ6Yqo4AcRPNq5aqrg4N4ot9sCxeDEnckbo8s7XPWqwDr4u8UfxVKRo= X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR11MB6163 X-OriginatorOrg: intel.com On Wed, Mar 05, 2025 at 05:21:21PM +0100, Alexander Lobakin wrote: > No idea what the current barrier position was meant for. At that point, > nothing is read from the descriptor, only the pointer to the actual one > is fetched. > The correct barrier usage here is after the generation check, so that > only the first qword is read if the descriptor is not yet ready and we > need to stop polling. Debatable on coherent DMA as the Rx descriptor > size is <= cacheline size, but anyway, the current barrier position > only makes the codegen worse. Makes sense: Reviewed-by: Maciej Fijalkowski But you know the process... :P fixes should go to -net. > > Fixes: 3a8845af66ed ("idpf: add RX splitq napi poll support") > Signed-off-by: Alexander Lobakin > --- > drivers/net/ethernet/intel/idpf/idpf_txrx.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c > index 6254806c2072..c15833928ea1 100644 > --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c > +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c > @@ -3232,18 +3232,14 @@ static int idpf_rx_splitq_clean(struct idpf_rx_queue *rxq, int budget) > /* get the Rx desc from Rx queue based on 'next_to_clean' */ > rx_desc = &rxq->rx[ntc].flex_adv_nic_3_wb; > > - /* This memory barrier is needed to keep us from reading > - * any other fields out of the rx_desc > - */ > - dma_rmb(); > - > /* if the descriptor isn't done, no work yet to do */ > gen_id = le16_get_bits(rx_desc->pktlen_gen_bufq_id, > VIRTCHNL2_RX_FLEX_DESC_ADV_GEN_M); > - > if (idpf_queue_has(GEN_CHK, rxq) != gen_id) > break; > > + dma_rmb(); > + > rxdid = FIELD_GET(VIRTCHNL2_RX_FLEX_DESC_ADV_RXDID_M, > rx_desc->rxdid_ucast); > if (rxdid != VIRTCHNL2_RXDID_2_FLEX_SPLITQ) { > -- > 2.48.1 >