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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: Pr0pjSnGBHTJVZ39x0SdV5A7aPVGJSkYpgpCi2b2LUkxy+yDnBEN0iD6+D8JFURHy3tS4cHKI0G3yujSFsTG5USgBIsXhPNGHON7vU46A6vGHPesMVzfpKex1EPTilwFZ60Htath5iodl8AzkdBbPzbgBKCdMlRancjJ7LOx5j2AenReKGiRWGYJvocItBtg12nmSv028e1jns38mqD/nzPcgiO2M6hcdmHA1cn7SYvLMSuKE3lD68EUJ19osp0/qqgTaPekAhE8G9FoXGY6BpD5LX5pU8ubkEy2T1+oD7/63KkjgwG8XG0X6+DfEQ22ZXk6IPQExavBPlh5LqZERNUH3X9F81F7O1j3ZjQAQYWXNH3N0k6K81KGn7iLlaZ95k9X+NdHNbxekaGaXWwEVTEV7nKLl9h1Akq0uj38baE7xIjeZ2cpamf0Jmv8to+l X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2026 15:34:18.2614 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 90366cab-3b1d-4165-7fbe-08df133ece84 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MW1PEPF0001615D.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS2PR12MB9749 From: Yishai Hadas __mlx5_ib_cq_clean() sweeps the CQ backwards from the producer index down to the consumer index: while ((int) --prod_index - (int) cq->mcq.cons_index >=3D 0) Both indexes are free running u32 counters, so the comparison has to be done modulo 2^32. Casting each operand to int and subtracting does not do that: the subtraction overflows whenever the two indexes straddle 2^31, which is undefined behaviour, and a compiler that assumes signed overflow cannot occur is free to discard the subtraction and fold the expression into a plain signed comparison. That comparison is not wraparound safe. The kernel is built with -fno-strict-overflow, so gcc and clang both retain the subtraction today and the generated code is unaffected; there is no known user-visible impact from the current code. Still, correctness here shouldn't depend on that build flag. Replace the loop with a plain unsigned equality check instead. while (prod_index !=3D cq->mcq.cons_index) { --prod_index; ... The preceding forward scan starts prod_index at cons_index and stops no later than cons_index + cq->ibcq.cqe, so the two indexes are at most cq->ibcq.cqe apart. Decrementing prod_index reaches cons_index in exactly that many iterations regardless of whether either counter has wrapped, because the loop no longer compares magnitudes at all. Signed-off-by: Yishai Hadas Signed-off-by: Edward Srouji --- drivers/infiniband/hw/mlx5/cq.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/mlx5/cq.c b/drivers/infiniband/hw/mlx5/c= q.c index 49b4bf148a4a017079c93a9b267690bf3a23169a..51892911e32a4b1c90c80e36c52= 3e1906feeab8b 100644 --- a/drivers/infiniband/hw/mlx5/cq.c +++ b/drivers/infiniband/hw/mlx5/cq.c @@ -1169,7 +1169,8 @@ void __mlx5_ib_cq_clean(struct mlx5_ib_cq *cq, u32 rs= n, struct mlx5_ib_srq *srq) /* Now sweep backwards through the CQ, removing CQ entries * that match our QP by copying older entries on top of them. */ - while ((int) --prod_index - (int) cq->mcq.cons_index >=3D 0) { + while (prod_index !=3D cq->mcq.cons_index) { + --prod_index; cqe =3D get_cqe(cq, prod_index & cq->ibcq.cqe); cqe64 =3D (cq->mcq.cqe_sz =3D=3D 64) ? cqe : cqe + 64; if (is_equal_rsn(cqe64, rsn)) { --=20 2.49.0 From nobody Fri Sep 25 07:21:57 2026 Received: from SA9PR02CU001.outbound.protection.outlook.com (mail-southcentralusazon11013046.outbound.protection.outlook.com [40.93.196.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DC6503B5314; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: NHfpuHuaut20jgjVztmAmE+u9VwQEn6xrNxaYa957W4vYAggaUEcam/8KtJwkrzh4Xq+GcNgxs4YOp4tkqgIdc0Kt8nJPvkt3NxklMKopchS2nZGEfh+0ciCzKzf36TEugM1y1uoo9Za96s0yFlfPK51ZaxFTZD5HmPd5iY4WpvSBNUpJiRuSvRSVzRhM+gfbsZgPFEDHBkwVNFNbXTf9K3oD9Ei8TBRhNS1xABwieZDygEUS/WL721TXCUVYAtEmHkbWa/7AXNqMA5lDf/K80qSDCnH38mW7BnYT1RBNUTg+mzZjm52iBmwIUyeDB6T5+jVn17gcc5gToqsWozH5iqdH0DyohYYExPcGKYYKmFr8Zrlx0mmnZ7U45waPcci6p4ycpg63Oi0yxO+YflqByK1OL87Z3r5BfeVfCx/duVStw1Po3ufH+FRkTljHTvO X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2026 15:34:16.7121 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 54d9eff0-074f-46ca-ad3b-08df133ecda6 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0002992D.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN7PPFFC4F04B28 From: Yishai Hadas __mlx4_ib_cq_clean() sweeps the CQ backwards from the producer index down to the consumer index: while ((int) --prod_index - (int) cq->mcq.cons_index >=3D 0) Both indexes are free running u32 counters, so the comparison has to be done modulo 2^32. Casting each operand to int and subtracting does not do that: the subtraction overflows whenever the two indexes straddle 2^31, which is undefined behaviour, and a compiler that assumes signed overflow cannot occur is free to discard the subtraction and fold the expression into a plain signed comparison. That comparison is not wraparound safe. The kernel is built with -fno-strict-overflow, so gcc and clang both retain the subtraction today and the generated code is unaffected; there is no known user-visible impact from the current code. Still, correctness here shouldn't depend on that build flag. Replace the loop with a plain unsigned equality check instead: while (prod_index !=3D cq->mcq.cons_index) { --prod_index; ... The preceding forward scan starts prod_index at cons_index and stops no later than cons_index + cq->ibcq.cqe, so the two indexes are at most cq->ibcq.cqe apart. Decrementing prod_index reaches cons_index in exactly that many iterations regardless of whether either counter has wrapped, because the loop no longer compares magnitudes at all. Signed-off-by: Yishai Hadas Signed-off-by: Edward Srouji --- drivers/infiniband/hw/mlx4/cq.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/mlx4/cq.c b/drivers/infiniband/hw/mlx4/c= q.c index 8879124697420c2ba03622c2af3b350808dc0aa2..98e3eb5cf96e54efdec6e4d8c58= 8fc865742337a 100644 --- a/drivers/infiniband/hw/mlx4/cq.c +++ b/drivers/infiniband/hw/mlx4/cq.c @@ -989,7 +989,8 @@ void __mlx4_ib_cq_clean(struct mlx4_ib_cq *cq, u32 qpn,= struct mlx4_ib_srq *srq) * Now sweep backwards through the CQ, removing CQ entries * that match our QP by copying older entries on top of them. */ - while ((int) --prod_index - (int) cq->mcq.cons_index >=3D 0) { + while (prod_index !=3D cq->mcq.cons_index) { + --prod_index; cqe =3D get_cqe(cq, prod_index & cq->ibcq.cqe); cqe +=3D cqe_inc; =20 --=20 2.49.0 From nobody Fri Sep 25 07:21:57 2026 Received: from PH7PR06CU001.outbound.protection.outlook.com (mail-westus3azon11010045.outbound.protection.outlook.com [52.101.201.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 55FA83BB132; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: rC0EgjpdCPuH1zU51O6oHUZ4T6tm6pA54KrYE8vEScyo0f/iAR8Z7zd2lOCNFaDtedAz+n9AtUMCFIAZWT0Tuwtfw3Iky26wwJKYSf0Av+a71KSNa1vUjnFfrD9Pyofe0a6pXn6NK8msf+nIl8I2OPT0z8rJZOXoOGRO3RXizBCD4zlhdxVbc6pPEGz/MtuhS1DU6CrkpEDwdGHKlvmfkZJjjfEErSbekdeFWZfGNVVf3SlMD5o7OX3ahpmUzWrpuwS6ny6Ed3K7WaNaC1Zw0ZZPWxz+KyBWT7ukF0MoaAouHnJxzTKhOmWzcy0zCNxX/B3lExI3Pg7c7nfkhLGgsIDmCwL7zbl9Ep3KH5rbez7Uo2CntqCUd44qEoAehPH48skJxYLhtvN5YvqqdQAxfSP26oCOLgVmaPZcU4DuVxgr1hbJ13zIV+badx/yE0pv X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2026 15:34:19.2601 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3c1699a4-4e01-422c-8e03-08df133ecf29 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0002992C.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB5603 From: Yishai Hadas mthca_cq_clean() sweeps the CQ backwards from the producer index down to the consumer index: while ((int) --prod_index - (int) cq->cons_index >=3D 0) Both indexes are free running u32 counters, so the comparison has to be done modulo 2^32. Casting each operand to int and subtracting does not do that: the subtraction overflows whenever the two indexes straddle 2^31, which is undefined behaviour, and a compiler that assumes signed overflow cannot occur is free to discard the subtraction and fold the expression into a plain signed comparison. That comparison is not wraparound safe. The kernel is built with -fno-strict-overflow, so gcc and clang both retain the subtraction today and the generated code is unaffected; there is no known user-visible impact from the current code. Still, correctness here shouldn't depend on that build flag. Replace the loop with a plain unsigned equality check instead: while (prod_index !=3D cq->cons_index) { --prod_index; ... The preceding forward scan starts prod_index at cons_index and stops no later than cons_index + cq->ibcq.cqe, so the two indexes are at most cq->ibcq.cqe apart. Decrementing prod_index reaches cons_index in exactly that many iterations regardless of whether either counter has wrapped, because the loop no longer compares magnitudes at all. Signed-off-by: Yishai Hadas Signed-off-by: Edward Srouji --- drivers/infiniband/hw/mthca/mthca_cq.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/mthca/mthca_cq.c b/drivers/infiniband/hw= /mthca/mthca_cq.c index 26c3408dcacaea9a0187257cc16de1b90f43fa40..39d4ff15849e7f8c2c3d47b4504= 306a4a4431c5d 100644 --- a/drivers/infiniband/hw/mthca/mthca_cq.c +++ b/drivers/infiniband/hw/mthca/mthca_cq.c @@ -300,7 +300,8 @@ void mthca_cq_clean(struct mthca_dev *dev, struct mthca= _cq *cq, u32 qpn, * Now sweep backwards through the CQ, removing CQ entries * that match our QP by copying older entries on top of them. */ - while ((int) --prod_index - (int) cq->cons_index >=3D 0) { + while (prod_index !=3D cq->cons_index) { + --prod_index; cqe =3D get_cqe(cq, prod_index & cq->ibcq.cqe); if (cqe->my_qpn =3D=3D cpu_to_be32(qpn)) { if (srq && is_recv_cqe(cqe)) --=20 2.49.0 From nobody Fri Sep 25 07:21:57 2026 Received: from CH4PR04CU002.outbound.protection.outlook.com (mail-northcentralusazon11013023.outbound.protection.outlook.com [40.107.201.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 691844AF69D; 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Tue, 15 Sep 2026 08:33:51 -0700 Received: from rnnvmail202.nvidia.com (10.129.68.7) by rnnvmail201.nvidia.com (10.129.68.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.46; Tue, 15 Sep 2026 08:33:50 -0700 Received: from [10.135.59.1] (10.127.8.10) by mail.nvidia.com (10.129.68.7) with Microsoft SMTP Server id 15.2.2562.46 via Frontend Transport; Tue, 15 Sep 2026 08:33:47 -0700 From: Edward Srouji Date: Tue, 15 Sep 2026 18:33:31 +0300 Subject: [PATCH rdma-next 4/4] RDMA/hns: Use unsigned comparison in the CQ cleanup loop Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-ID: <20260915-fix-cq-cleanup-v1-4-e991944cf898@nvidia.com> References: <20260915-fix-cq-cleanup-v1-0-e991944cf898@nvidia.com> In-Reply-To: <20260915-fix-cq-cleanup-v1-0-e991944cf898@nvidia.com> To: Leon Romanovsky , Jason Gunthorpe , "Nathan Chancellor" , Nick Desaulniers , Bill Wendling , Justin Stitt , Yishai Hadas , Chengchang Tang , Junxian Huang CC: , , , Edward Srouji X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: TCNjhlqfyre6CjOSnpHTsYTd3ompa67wKFl6W4z8B5zuhCrIuuWQDPifimGmBq6oSV+1RJZ7Tg8TTNEsT9HW1g6msy/gM+Y/o++vxSd9l/O5JKK4haeHA9Toz4zy7K5V0wZgH/2kBshjyLvTB2aLYFnnx/J6MvI/xc2x5F1aP1i9Hiztr9Iv4KdTdEYGdz3A6bk/58J5Wolo5iUtU08pCiYwuguY77le9DhTfVm4Yjt+sRW21XaWcGTj5KfbGFW6EAdUsajXRevDBr5YKz/YY1fRId3OYZwwlH7GJCUv/f4hWcAv/GWDmotNwlB8anqsCi5PcAkNKs4wpD/NRpf46LNi+0G+QWYNOHnolsmLIGPGcvFYN2hS7yilWM0MRG5d6qPwuaX6+ScZ26q67RDIEEb0GuImg6v+6nCTJ/4G0ASh8AitD0G6SAxsJtJX9xNl X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2026 15:34:27.6045 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d68ea436-c05b-421f-1ac7-08df133ed40c X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MW1PEPF0001615A.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB7643 From: Yishai Hadas __hns_roce_v2_cq_clean() sweeps the CQ backwards from the producer index down to the consumer index: while ((int) --prod_index - (int) hr_cq->cons_index >=3D 0) Both indexes are free running u32 counters, so the comparison has to be done modulo 2^32. Casting each operand to int and subtracting does not do that: the subtraction overflows whenever the two indexes straddle 2^31, which is undefined behaviour, and a compiler that assumes signed overflow cannot occur is free to discard the subtraction and fold the expression into a plain signed comparison. That comparison is not wraparound safe. The kernel is built with -fno-strict-overflow, so gcc and clang both retain the subtraction today and the generated code is unaffected; there is no known user-visible impact from the current code. Still, correctness here shouldn't depend on that build flag. Replace the loop with a plain unsigned equality check instead: while (prod_index !=3D hr_cq->cons_index) { --prod_index; ... The preceding forward scan starts prod_index at cons_index and advances it only while get_sw_cqe_v2() still reports a software owned entry, so the two indexes stay within one CQ's worth of entries. Decrementing prod_index reaches cons_index in exactly that many iterations regardless of whether either counter has wrapped, because the loop no longer compares magnitudes at all. Signed-off-by: Yishai Hadas Signed-off-by: Edward Srouji --- drivers/infiniband/hw/hns/hns_roce_hw_v2.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c b/drivers/infiniban= d/hw/hns/hns_roce_hw_v2.c index 1b2504301ebea4279eb0dcb2537c3574d0122d95..35be5b038f6861f1c330739f5c9= 7817a4c3940a7 100644 --- a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c @@ -3828,7 +3828,8 @@ static void __hns_roce_v2_cq_clean(struct hns_roce_cq= *hr_cq, u32 qpn, * Now backwards through the CQ, removing CQ entries * that match our QP by overwriting them with next entries. */ - while ((int) --prod_index - (int) hr_cq->cons_index >=3D 0) { + while (prod_index !=3D hr_cq->cons_index) { + --prod_index; cqe =3D get_cqe_v2(hr_cq, prod_index & hr_cq->ib_cq.cqe); if (hr_reg_read(cqe, CQE_LCL_QPN) =3D=3D qpn) { if (srq && hr_reg_read(cqe, CQE_S_R)) { --=20 2.49.0