From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3AB3E2472B5; Fri, 12 Sep 2025 10:42:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757673732; cv=none; b=nNYqd8hQZTALljxqnVDlWJPhwp/svQWmqyQy8EN5lyjpTQN2hb8oIEJj51zbwF3+j22awQsOrm4cLSBRvdfdvYE04E855t5s+wAWK2VkdeDu1zbC8S698YxMJRAGxKVRBJCObiL6yiXnwr/dnKpI5Eh9B12PjY2QUYa1DVhB9aE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757673732; c=relaxed/simple; bh=otd6QxpT8qFQVUNAzfILUI02V9sOlrSc4wYVCCapfTg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=D8FMeeYnYrmwEn6qfRUFXrTnlbhTQF47mc+7jOVzksTyYBdqZcAVUatN4eFz76q3XOxE1vlggchF8UAKa4diYqvOH76OCUdYt643UHW5s+wBJzGwQT/Zj18WtPoiBadRR9GXcq/ukNvmfr7I2mIe0oNdjLSerkfRDTSPInJue1A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 437FA1515; Fri, 12 Sep 2025 03:42:02 -0700 (PDT) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 505263F66E; Fri, 12 Sep 2025 03:42:05 -0700 (PDT) Message-ID: <13347819-c83d-446b-856e-d7fd8ec742ea@arm.com> Date: Fri, 12 Sep 2025 11:42:03 +0100 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 10/29] arm_mpam: Add cpuhp callbacks to probe MSC hardware To: James Morse , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org Cc: D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , fenghuay@nvidia.com, baisheng.gao@unisoc.com, Jonathan Cameron , Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich , Lecopzer Chen References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-11-james.morse@arm.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <20250910204309.20751-11-james.morse@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi James, On 9/10/25 21:42, James Morse wrote: > Because an MSC can only by accessed from the CPUs in its cpu-affinity > set we need to be running on one of those CPUs to probe the MSC > hardware. > > Do this work in the cpuhp callback. Probing the hardware will only > happen before MPAM is enabled, walk all the MSCs and probe those we can > reach that haven't already been probed as each CPU's online call is made. > > This adds the low-level MSC register accessors. > > Once all MSCs reported by the firmware have been probed from a CPU in > their respective cpu-affinity set, the probe-time cpuhp callbacks are > replaced. The replacement callbacks will ultimately need to handle > save/restore of the runtime MSC state across power transitions, but for > now there is nothing to do in them: so do nothing. > > The architecture's context switch code will be enabled by a static-key, > this can be set by mpam_enable(), but must be done from process context, > not a cpuhp callback because both take the cpuhp lock. > Whenever a new MSC has been probed, the mpam_enable() work is scheduled > to test if all the MSCs have been probed. If probing fails, mpam_disable() > is scheduled to unregister the cpuhp callbacks and free memory. > > CC: Lecopzer Chen > Signed-off-by: James Morse > --- > Changes since v1: > * Removed register bounds check. If the firmware tables are wrong the > resulting translation fault should be enough to debug this. > * Removed '&' in front of a function pointer. > * Pulled mpam_disable() into this patch. > * Disable mpam when probing fails to avoid extra work on broken platforms. > * Added mpam_disbale_reason as there are now two non-debug reasons for this > to happen. Looks good to me. Reviewed-by: Ben Horgan Thanks, Ben