From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ms.lwn.net (ms.lwn.net [45.79.88.28]) (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 50DAA1A6808; Sun, 3 May 2026 15:16:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.79.88.28 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777821367; cv=none; b=pZj3C/4H7VIfUL4TZoyN+yT/2oKLpXRpNe+oOotqMvPze9IkElxX8zDzBpdJqBQWn5dH1wkOx/JMBhXNUG7PrRS9+wcNxWo5P+hQ+NBmbQc6MwwpUuVBzws4MwWFrO43wZTCjtA1OkxOYPblmTkXfgay2zjYT9r2M9iS3yaVmYk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777821367; c=relaxed/simple; bh=FrQTgFh5xBirNB3V0+ic1VfjdTXAM3RePlrK+PRicyQ=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=HuijII0N/ceJYam/oKCvMxIDcOmdAz8+q8EDjnT23TX2q6vTWsHSxuSMtgu2dbpc/cVEMZDK388g8/qQLd7HxAYDlB38Li3Vuh+gaBk1x6tfUAyZsqzCq+7HQjtgrxxT+s35zF+705QZfDACcsDVXiHcXKexJHP62bkOAcpdW7Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lwn.net; spf=pass smtp.mailfrom=lwn.net; dkim=pass (2048-bit key) header.d=lwn.net header.i=@lwn.net header.b=cfzdDUHZ; arc=none smtp.client-ip=45.79.88.28 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lwn.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lwn.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=lwn.net header.i=@lwn.net header.b="cfzdDUHZ" DKIM-Filter: OpenDKIM Filter v2.11.0 ms.lwn.net 131D041084 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lwn.net; s=20201203; t=1777821365; bh=xHtiiDrFaA5dwViXPQT0TECpzX0/1YLefV9TvY+Kca4=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=cfzdDUHZ4ysmxcxlb5UIH2LmUzmTS8DOhKD6sQ13tlLhC+ayQ4wC1/pZQ8QUI/z5O WAyvU2wEvw5DTKUeQtfextYEtylNVOyLeNWl22YB+mFWyDEVyarEmKmoLnrDlRSpwr yK+7VxT59Xouz+Ls2xYbm55rDPofU5EjxgI6QLbu32gdntWceYXtLOygCSpUF9jYYX c51Yal5d7E7GW0sgGzGQmLjilzToGC+qr1jLsDE0IH77y4JnV2krzT6SMA+DR9xfZ0 7baeBQh7nfkuscaLxUSP/O4WEOy22oJNNuhusWxR1GrwisETSAXGYQLKUBYRSNABYH b//q8tTJX515Q== Received: from localhost (mdns.lwn.net [45.79.72.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by ms.lwn.net (Postfix) with ESMTPSA id 131D041084; Sun, 3 May 2026 15:16:04 +0000 (UTC) From: Jonathan Corbet To: Aaron Tomlin , skhan@linuxfoundation.org Cc: tglx@kernel.org, akpm@linux-foundation.org, bp@alien8.de, rdunlap@infradead.org, dave.hansen@linux.intel.com, feng.tang@linux.alibaba.com, pawan.kumar.gupta@linux.intel.com, dapeng1.mi@linux.intel.com, kees@kernel.org, elver@google.com, paulmck@kernel.org, lirongqing@baidu.com, bhelgaas@google.com, bigeasy@linutronix.de, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] docs: kernel-parameters: document scope of irqaffinity= parameter In-Reply-To: <20260421150911.42404-1-atomlin@atomlin.com> References: <20260421150911.42404-1-atomlin@atomlin.com> Date: Sun, 03 May 2026 09:16:01 -0600 Message-ID: <87y0i0bk26.fsf@trenco.lwn.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Aaron Tomlin writes: > There is a common misconception that the "irqaffinity=" boot parameter > acts as a global override for all hardware interrupts. In reality, it > only sets the irq_default_affinity mask, which is explicitly ignored > by managed interrupts (e.g., modern multiqueue storage controllers). > > This patch updates kernel-parameters.txt to document this limitation, > directs users to "isolcpus=managed_irq" and > Documentation/core-api/irq/managed_irq.rst for further details. > Additionally, it updates managed_irq.rst to provide a debugfs example > demonstrating the IRQD_AFFINITY_MANAGED state flag. > > Signed-off-by: Aaron Tomlin > --- > Changes in v1 [1]: > - Provided an example of a managed IRQ using CONFIG_GENERIC_IRQ_DEBUGFS > - Referenced Documentation/core-api/irq/managed_irq.rst > > [1]: https://lore.kernel.org/lkml/20260414200245.1153919-1-atomlin@atomlin.com/ > --- > .../admin-guide/kernel-parameters.txt | 11 ++++ > Documentation/core-api/irq/managed_irq.rst | 53 ++++++++++++++++++- > 2 files changed, 62 insertions(+), 2 deletions(-) [...] > diff --git a/Documentation/core-api/irq/managed_irq.rst b/Documentation/core-api/irq/managed_irq.rst > index 05e295f3c289..8e973a7d1bd1 100644 > --- a/Documentation/core-api/irq/managed_irq.rst > +++ b/Documentation/core-api/irq/managed_irq.rst > @@ -80,9 +80,58 @@ The following examples assume a system with 8 CPUs. > /proc/irq/48/effective_affinity_list:0 > /proc/irq/48/smp_affinity_list:7 > > - This can be verified via the debugfs interface > - (/sys/kernel/debug/irq/irqs/48). The dstate field will include > + If the Linux kernel was built with Kconfig CONFIG_GENERIC_IRQ_DEBUGFS > + enabled, this can be verified via the debugfs interface (e.g., > + /sys/kernel/debug/irq/irqs/48). The dstate field will include > IRQD_IRQ_DISABLED, IRQD_IRQ_MASKED and IRQD_MANAGED_SHUTDOWN. > + A managed IRQ will also include IRQD_AFFINITY_MANAGED. For example: > + > + # cat /sys/kernel/debug/irq/irqs/87 > + handler: handle_edge_irq > + device: 0000:41:00.0 This will not render the way you seem to expect, it should be a literal block. Please do build the docs and look at the results before sending documentation patches. Thanks, jon