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mx.microsoft.com 1; spf=pass smtp.mailfrom=atomlin.com; dmarc=pass action=none header.from=atomlin.com; dkim=pass header.d=atomlin.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=atomlin.com; Received: from CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:183::5) by CWLP123MB4179.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:be::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.406.9; Thu, 10 Sep 2026 16:43:08 +0000 Received: from CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM ([fe80::cec4:77ab:262e:d230]) by CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM ([fe80::cec4:77ab:262e:d230%4]) with mapi id 15.21.0406.007; Thu, 10 Sep 2026 16:43:08 +0000 From: Aaron Tomlin To: axboe@kernel.dk, tglx@kernel.org, aacraid@microsemi.com, James.Bottomley@HansenPartnership.com, mkp@kernel.org, frederic@kernel.org, bigeasy@linutronix.de Cc: atomlin@atomlin.com, ionut.nechita@windriver.com, corbet@lwn.net, vincent.guittot@linaro.org, mingo@redhat.com, peterz@infradead.org, radu@rendec.net, akpm@linux-foundation.org, steve@abita.co, sean@ashe.io, chjohnst@gmail.com, neelx@suse.com, mproche@gmail.com, nick.lange@gmail.com, marco.crivellari@suse.com, rishil1999@outlook.com, linux-doc@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v16 5/9] isolation: Introduce managed_irq_strict isolcpus type Date: Thu, 10 Sep 2026 12:42:33 -0400 Message-ID: <20260910164237.500196-6-atomlin@atomlin.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260910164237.500196-1-atomlin@atomlin.com> References: <20260910164237.500196-1-atomlin@atomlin.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: BN9PR03CA0887.namprd03.prod.outlook.com (2603:10b6:408:13c::22) To CWLP123MB6607.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:183::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB6607:EE_|CWLP123MB4179:EE_ X-MS-Office365-Filtering-Correlation-Id: cb32cc82-6055-477a-f199-08df0f5a97b1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|23010399003|366016|10067099003|56012099006|6133799003|3023799007|18002099003|22082099003; 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However, these drivers are not aware of CPU isolation requirements and will distribute queues and interrupt vectors without considering the isolcpus configuration. The existing isolcpus=managed_irq parameter attempts post-allocation affinity steering, but this is best-effort and fails on modern multiqueue storage where the number of queues meets or exceeds the CPU count. Introduce a new isolcpus flag, "managed_irq_strict", that allows users to strictly define which CPUs should have multiqueue hardware queues and managed interrupts assigned. This enforces pre-allocation queue bounding and mask exclusion, preventing managed hardware interrupts from ever targeting isolated cores. Because managed_irq_strict is a strict superset of managed_irq, specifying managed_irq_strict automatically enables HK_FLAG_MANAGED_IRQ as well. This ensures subsystems that rely on managed interrupt isolation (e.g. Hyper-V VMBus channel distribution) continue to function seamlessly. Signed-off-by: Daniel Wagner Reviewed-by: Martin K. Petersen Reviewed-by: Hannes Reinecke Signed-off-by: Aaron Tomlin --- include/linux/sched/isolation.h | 1 + kernel/sched/isolation.c | 16 ++++++++++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h index cf0fd03dd7a2..bda3003ce86f 100644 --- a/include/linux/sched/isolation.h +++ b/include/linux/sched/isolation.h @@ -18,6 +18,7 @@ enum hk_type { HK_TYPE_MANAGED_IRQ, /* Inverse of boot-time nohz_full= or isolcpus=nohz arguments */ HK_TYPE_KERNEL_NOISE, + HK_TYPE_MANAGED_IRQ_STRICT, HK_TYPE_MAX, /* diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 9f02e9264a3f..7e9e78a18fb9 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -17,6 +17,7 @@ enum hk_flags { HK_FLAG_DOMAIN = BIT(HK_TYPE_DOMAIN), HK_FLAG_MANAGED_IRQ = BIT(HK_TYPE_MANAGED_IRQ), HK_FLAG_KERNEL_NOISE = BIT(HK_TYPE_KERNEL_NOISE), + HK_FLAG_MANAGED_IRQ_STRICT = BIT(HK_TYPE_MANAGED_IRQ_STRICT), }; DEFINE_STATIC_KEY_FALSE(housekeeping_overridden); @@ -354,6 +355,12 @@ static int __init housekeeping_isolcpus_setup(char *str) continue; } + if (!strncmp(str, "managed_irq_strict,", 19)) { + str += 19; + flags |= HK_FLAG_MANAGED_IRQ_STRICT; + continue; + } + /* * Skip unknown sub-parameter and validate that it is not * containing an invalid character. @@ -374,6 +381,15 @@ static int __init housekeeping_isolcpus_setup(char *str) str++; } + /* + * managed_irq_strict is a strict superset of managed_irq. + * Ensure that HK_FLAG_MANAGED_IRQ is also set so that subsystems + * relying on managed interrupt isolation (e.g. Hyper-V VMBus channel + * distribution and CPU hotplug IRQ restoration) continue to function. + */ + if (flags & HK_FLAG_MANAGED_IRQ_STRICT) + flags |= HK_FLAG_MANAGED_IRQ; + /* Default behaviour for isolcpus without flags */ if (!flags) flags |= HK_FLAG_DOMAIN | HK_FLAG_DOMAIN_BOOT; -- 2.55.0