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 F27012222AF; Mon, 29 Sep 2025 17:44:22 +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=1759167865; cv=none; b=JKwskMl7hUcbWsRs0yEY+lIOvEwolP3h9tICCrSdRpnspIEbxhDk4+jnZ92UQIASMGLesg5zM68GnkYulSF5bqG0YL5DGcu8xmdyou8gDXuwWqZ/EjSuJWWw775al9hbRLMrz5ZFhAdAzyWpEbRvEWDPxdt7idW0CnA9t4DOP2E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759167865; c=relaxed/simple; bh=oLEs3M/HoMQmClNW65g0NyCg7T9r85p1Tp75aPNj8EI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qdwVhwd+/Wvhw8rEO1/W3HoodIp4h6ObUiLa+9Au7efP+TiDMTubCphwP166sJDfT344+FJF83oQSsLf/UPOAx4gREJoynsobt5BCoiA738FcTSOroSUMHgI7T+FMUDaZ3nzqRY+C9iv7JwB4aVhST8WgO+egqFuYtVmVQoB9xU= 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 EDB2F1758; Mon, 29 Sep 2025 10:44:13 -0700 (PDT) Received: from [10.1.197.69] (eglon.cambridge.arm.com [10.1.197.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AC47F3F59E; Mon, 29 Sep 2025 10:44:16 -0700 (PDT) Message-ID: <59fbb8d9-5df6-4269-aa81-147618450644@arm.com> Date: Mon, 29 Sep 2025 18:44:16 +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: Ben Horgan , 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> <13347819-c83d-446b-856e-d7fd8ec742ea@arm.com> Content-Language: en-GB From: James Morse In-Reply-To: <13347819-c83d-446b-856e-d7fd8ec742ea@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Ben, On 12/09/2025 11:42, Ben Horgan wrote: > 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! James