From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 822A0C43327 for ; Thu, 2 Jul 2026 16:22:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=9xukYNJK6y2HUYwEJZJvxcGbFnpLpQIbOyJ7olcEeJE=; b=UZ1kkQc29ZGoUeqtLydwyUUrGf X9PO/AOWgSTDR3R+MKBkmRIL7xx3yirG157JSTkE0EfRoJhsdt2qSZRcFe5oxDU5pHfnL1IaWennS NmEulpqQ7yjLaV8maGH7v6xjfxO4vJN6LPB55/0ikBGwnLX/OITD7el5EU5afbgpw9+oXc9fNINlk do2qIiWvW1XXqKKk/33o4ljqehxBs8D/7gbF+Yows3VPFjR1QInTsl4+0eja3qyLw54hhP8tSgm50 rgjFo9h0tnG3FhpdsQefHy9WLbGyk26Gq8Helat+VJh//bJzLhc2npPO8ckiZr27EeHZ5nYeJrNtW z5qJJMqQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wfKBY-00000004zEG-0HFU; Thu, 02 Jul 2026 16:22:44 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wfKBV-00000004zDj-29xM for linux-arm-kernel@lists.infradead.org; Thu, 02 Jul 2026 16:22:42 +0000 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 1B76D35C8; Thu, 2 Jul 2026 09:22:35 -0700 (PDT) Received: from e142021.fritz.box (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B73583F673; Thu, 2 Jul 2026 09:22:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783009359; bh=jx+Qd7AP+X/MGpo14TPEW2DjAqmqN8QLFvZbq4wW3sQ=; h=From:To:Cc:Subject:Date:From; b=twZjVC44HzKULb6/gEAEpWzlbxJONCyeiIXJDQBzbGBbo3/BLCUkjX9IRF51SApbg nfZYjie6upQUpTusodB5em1enfFReEbdnYlqWf8tGGA4uJIDQSGBXX/rq+kq+iXPEk 5/I+M0TO8inJFj1M28XtqPtAIbsgp8d9XOrNc/fs= From: Andre Przywara To: Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Ben Horgan , Reinette Chatre , Fenghua Yu Cc: Jonathan Cameron , Srivathsa L Rao , Ganapatrao Kulkarni , Trilok Soni , Srinivas Ramana , Niyas Sait , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 00/15] arm_mpam: Add MPAM-Fb firmware support Date: Thu, 2 Jul 2026 18:22:14 +0200 Message-ID: <20260702162229.4008659-1-andre.przywara@arm.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260702_092241_649170_E1AB6FB9 X-CRM114-Status: GOOD ( 26.86 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, version 2 of the MPAM-Fb code, for firmware based MSC accesses. Major change is a rudimentary propagation of errors during the MSC accesses, this has been split up into 11 patches, coming first in this series. The patch to parse additional information from the ACPI table has been dropped (former patch 1/5), as it's actually not needed for MPAM-Fb, and the features parsed are not supported by the kernel yet. Quite some details have been fixed in the remaining patches, thanks to the diligent reviewers. This should address most of the comments, but I am pretty sure this won't be the final version ;-) Find a changelog below. Based on v7.2-rc1. ======================= The Arm MPAM specification defines Memory System Components (MSCs), which are devices that are programmed through an MMIO register frame. In some occasions this turned out to be too limiting: the MSC might be located behind a separate bus system (for instance inside an on-board controller), it might be mapped secure-only, or in a different processor socket without direct MMIO mapping. Also the MMIO access might be too slow or it would need to be filtered or otherwise access controlled. Finally there might be bugs in the MSC integration, which require a mediating firmware to be accessible. To accommodate all those different use cases, the MPAM-Fb specification [1] describes an alternative way to access MSCs. Accesses to an MSC would be wrapped in a message and communicated to the system using a shared-memory/mailbox system mostly mimicking the Arm SCMI spec. For ACPI systems, this would be abstracted through an ACPI PCC channel, which provides the shared-memory region and the mailbox trigger. We can lean on existing ACPI parsing code to register with these two subsystems, but cannot rely on the existing SCMI code in the kernel. This means we somewhat need to open code a very simplified SCMI handler, which just provides enough functionality for the very basic subset of SCMI that the MPAM-Fb spec requires. The first 11 patches rework all MSC access wrappers to propagate error information. Pure MMIO based MSC accesses would never fail, but the MPAM-Fb access can go wrong in multiple ways. The patches have been split up purely for reviewing reasons, if the number is a problem, we could as well squash them. Patch 12/15 solves a nasty problem: At the moment we protect stateful MSC register accesses (mon_sel) through a spinlock. Unfortunately the mailbox subsystem and the slow nature of the communication through this channel forbid MPAM-Fb access in atomic context. So this patch splits the lock in two: the "outer" one is a mutex, and only the inner one is a spinlock, which would need to be taken when programming MSCs inside an interrupt handler, for instance. We just deny the latter when using MPAM-Fb, ideally we wouldn't need that (no need to IPI another core when the MSC access does not need to be local to one particular core), or we simply deny that part of the functionality (access through perf). Patch 13/15 adds the code to redirect MSC accesses through the PCC shmem/mailbox system. Patch 14/15 avoids the error IRQ handler to do an MSC access when using MPAM_Fb, since those accesses cannot run in atomic context. The final patch 15/15 then adds the code to detect and store the PCC channel information from the ACPI tables, and eventually enables MPAM-Fb accesses. This would enable systems where some MSCs are not accessible via MMIO to use those components anyway. Please have a look and test! Cheers, Andre [1] https://developer.arm.com/documentation/den0144/latest Changelog v1 .. v2: - add patches to add error propagation to MSC access wrappers - drop former patch 1/5 (not needed) - drop lock in mpam_reprogram_msc(), to avoid double lock - add support for multiple MSCs per PCC channel - adjust SCMI protocol code to use a PCC subtype 3 channel - let PCC code handle the PCC channel negotiation (due to subtype 3) - drop SCMI names in shmem offsets, and use existing PCC type 3 struct - adjust shmem field offsets to match MPAM-Fb spec, not pure SCMI - prevent MPAM-Fb calls inside atomic smp_call_function_any() payload - skip all MSC accesses inside the IRQ handler when using MPAM-Fb Andre Przywara (14): arm_mpam: let low level MSC read accessors return an error arm_mpam: propagate MSC read errors for wrapper functions arm_mpam: propagate MSC read errors for hw_probe functions arm_mpam: propagate MSC read errors for mpam_msc_read_mbwu_l() arm_mpam: propagate MSC read errors for msmon helpers arm_mpam: propagate MSC read errors for __ris_msmon_read() arm_mpam: propagate MSC read errors for state saving functions arm_mpam: let low level MSC write accessors return an error arm_mpam: propagate MSC write errors for ESR and part_sel wrappers arm_mpam: propagate MSC write errors for hardware probe functions arm_mpam: propagate MSC write errors for remaining MSC write users arm_mpam: add MPAM-Fb MSC firmware access support arm_mpam: prevent MPAM-Fb accesses inside IRQ handler arm_mpam: detect and enable MPAM-Fb PCC support James Morse (1): arm_mpam: Split the locking around the mon_sel registers drivers/acpi/arm64/mpam.c | 2 + drivers/resctrl/Makefile | 2 +- drivers/resctrl/mpam_devices.c | 630 ++++++++++++++++++++++++-------- drivers/resctrl/mpam_fb.c | 137 +++++++ drivers/resctrl/mpam_fb.h | 17 + drivers/resctrl/mpam_internal.h | 79 +++- include/linux/arm_mpam.h | 2 +- 7 files changed, 688 insertions(+), 181 deletions(-) create mode 100644 drivers/resctrl/mpam_fb.c create mode 100644 drivers/resctrl/mpam_fb.h base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 -- 2.43.0