From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 D24C243CEC1 for ; Tue, 4 Aug 2026 08:56:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785833815; cv=none; b=fPIKoINMJ7PipW6wqTSs0dAanXGC/HCyGZQvFZS1OqIHPbn7XghTf95QWNPqDOI4Cr16unDZzK4RzRYXXuKwloQQnU7foLIXsbS7Qut1dDcK/deGBhg0q0nQLli2WyJhfj5a1N52c12h4Pr2ZLmXOAVgwAGkQlDTwaOdgN5rveY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785833815; c=relaxed/simple; bh=h6wQ/gBgYU8sEnHG7gKIOXfVVIysv10bJ53XQ7jVs+U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hDg6262CN+sdXaQOfJP9SPiXpf9xn0LzLGQL/elAnTLYaKFyxhc9Vd7CYnQWpi58o4aOmBy15e9VZMKYPtiA5piZf3dce6YpSsKRhVEp+HQvzGJVLuh/fHncHiRbolXjQO3euqlV3hVVY5rE4XmnLUDw9NN01yb0v/Gv17CbdSs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=aQD1prZ0; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=qa+FYKMs; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="aQD1prZ0"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="qa+FYKMs" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785833812; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oHMZ+hX0V0vr0a9Nft0AKjYbaEjQK6WSHNPIE5IxYn0=; b=aQD1prZ0/iwJo1Rx0E/nCx0O1b+TuXXTw5Y8yVtLOUIpkvjSQo0xdV7C+VO+YBWVqYTDaO /ZV9K7+DQmKdhQZVnyeOsxwGkssW6dNkeGvhiQPA11rQz5Qi+9I4JPnDzgdCumzZ4JFqrC dL6QZ5eNt+yiZ9LURWkIj7VMKwsvEIc= Received: from mail-pl1-f197.google.com (mail-pl1-f197.google.com [209.85.214.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-47-gBrbvSx1OTCmdaX-SOmVZQ-1; Tue, 04 Aug 2026 04:56:51 -0400 X-MC-Unique: gBrbvSx1OTCmdaX-SOmVZQ-1 X-Mimecast-MFC-AGG-ID: gBrbvSx1OTCmdaX-SOmVZQ_1785833811 Received: by mail-pl1-f197.google.com with SMTP id d9443c01a7336-2cacf17c7e0so55204435ad.0 for ; Tue, 04 Aug 2026 01:56:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1785833810; x=1786438610; darn=vger.kernel.org; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to :content-type; bh=oHMZ+hX0V0vr0a9Nft0AKjYbaEjQK6WSHNPIE5IxYn0=; b=qa+FYKMs94Wz7+hHqk/fs7+A/V4aOA/BLKLnK12ZMXvgNYOz+dL+yW0FQmRZuOkGSl pNKkcmNrOYHqNfx56VxEBZxSvMwZ5sy1/CyC47ar364fCIPlVnLJi8R3RzgUVxdksQJo eFM+oLo0BtUUXRkB+sCiY7rGZgxJH5v9oFUI0Wnl2VOWOtY8zP+bpmezrOMOjRMkwZmF /oWKq01ZRZUptJUH+TQi+WYu2oF93QwwK1D7OVR+uIbkbC3WXAJS5LPHBNfoyHrwK7DV Z4/cvKXTRQqSz7RjbWwSRfnDA5cRz4z2pQXTbTlFPXLiTCF466HINmCglxbnLjYFfBjh 9N5A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785833810; x=1786438610; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=oHMZ+hX0V0vr0a9Nft0AKjYbaEjQK6WSHNPIE5IxYn0=; b=rUwzDNxIOUff9jSloSAfmVYb1IroLZ6bUu1VYbw9zW/GNpkpIMJpgePtlRsBCnmNE/ l9mqu4/6h2SndP+cZR997amol3YufHWzYz9EqD+91e1wY90+8zhxSerrkaUK18rS3DZX JS64vpwiL7g/3XTsTeAnW2FQNWPo83hNFAq3X33Etr5nXE2MB5x3hUOlTskuhWg1sQuH 3/wgOYqVpH9PZlurqLRldQ3mCvlC4XtsydtKVYCkOYSQiUdMe39MqjVQPEAdklcakRPK s6PnO0PMM/eBKjt/28ZvCn1vvyi6NcpHxnUZ1QfKYOEEbwJIseDYAocpNkLcOxJvyklE H1Xw== X-Forwarded-Encrypted: i=1; AHgh+RrdCSLJoM5a1jxqi6JZtWB0FMIEzG1Ow1W/ZjU6+9X/hHtuG01Pt9IQgYu/LduFHRlw6n7iicXh8ZNpIaA=@vger.kernel.org X-Gm-Message-State: AOJu0YxkYLysrAtf7bh1lp/ZEXw7AyoMPmi0IHEptBYP78/L1BV/GiAp jp2vppGNdrnmEgVSMvr+AHzwB8REse1WCq/jZwr3FM5Gl0oMDdAm6tij9xX5GTpL8Hrr1PMBnoP Xv4aCiu1S6jCH72Lix90bupC4YabVAIcohzMgFTvCo77BkV2Q9FwXhY3YmGrwWZNtgQ== X-Gm-Gg: AR+sD11iRF12qrdHJUe4snrBF4lg/ts/vKIyupHmnnwtjeBt0F1WG2O9jEzRJmBvo4f yzI/+DfVY7DuS2oynZsOZZkcDpc4SsDe+t+QeXubj/Un18kIX3lo/+eymeiCvPdEM9uBcrvk+ig jr5kQ0tHOVfhaj0UxwY1Uo9uqkDUhBV/IPQeXbtlGOJHrN09I2l0bAYYEbYQHtfnVUwzoH4FYeP bjVhBH1qJ7j0idFiaxI5D40eMVViEZYJDXNU9eY9Cr62GM8zIYn2t0rgijU+v4EZ11+zP6DJwFC QNmmLngRWPuY/nsdhQ3KjUKfast2RxTwIi8ndWMD5u1ZvnXMywFyy4jOKNIv1/apSJW34L5KjLm 5jrvLWxAu4vCEXCDfMnB3HorhUgFUVKAfJgQmLPlq8Uo= X-Received: by 2002:a17:902:d48f:b0:2ca:bf8e:35fe with SMTP id d9443c01a7336-2d0521e2704mr122370715ad.16.1785833810464; Tue, 04 Aug 2026 01:56:50 -0700 (PDT) X-Received: by 2002:a17:902:d48f:b0:2ca:bf8e:35fe with SMTP id d9443c01a7336-2d0521e2704mr122370395ad.16.1785833809903; Tue, 04 Aug 2026 01:56:49 -0700 (PDT) Received: from [192.168.68.51] (n175-34-8-244.mrk21.qld.optusnet.com.au. [175.34.8.244]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d0aa4d9b86sm2899145ad.76.2026.08.04.01.56.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Aug 2026 01:56:49 -0700 (PDT) Message-ID: <8a5e291f-f547-4dad-8a90-1ebb1511a280@redhat.com> Date: Tue, 4 Aug 2026 18:56:37 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 00/11] arm_mpam: Add MPAM-Fb firmware support To: Andre Przywara , 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 , Lee Trager , Ritwick Sharma , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260731170324.2927758-1-andre.przywara@arm.com> <6f8bc358-91a0-4c44-9110-c071e10df385@redhat.com> Content-Language: en-US From: Gavin Shan In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Andre, On 8/4/26 6:50 PM, Andre Przywara wrote: > Hi Gavin, > > many thanks for the review and the testing! > > ... > > On 8/4/26 05:29, Gavin Shan wrote: >> On 8/1/26 3:03 AM, Andre Przywara wrote: >>> v7 is another quick respin of the MPAM-Fb code, for firmware based MSC >>> accesses. This propagates MSC access errors in a function where it was >>> missing before, covering more functions that pass their return value >>> to userspace (new patch 07/11). Also some bug fixes, formatting >>> adjustments and adding the accumulated tags - many thanks to the >>> reviewers. Find the 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 seven 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. Please note that until the very last patch of this series >>> any MSC accesses would always only return 0, it's only the final enablement >>> of MPAM-Fb that could possibly introduce errors. Hence all former patches >>> can add error handling gradually, those code paths wouldn't be triggered >>> before patch 11/11. >>> Patch 8/11 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 keeps using a >>> spinlock for MMIO based accesses, but reverts to a mutex otherwise. >>> We just deny taking the lock for MPAM-Fb in atomic context, 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 9/11 adds the code to redirect MSC accesses through the >>> PCC shmem/mailbox system. >>> Patch 10/11 reworks the error interrupt handler to use a threaded IRQ for >>> MPAM-Fb, to be able to do MPAM-Fb MSC accesses inside (which might sleep). >>> The final patch 11/11 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 >>> >>> Changes in v7: >>> - add tags >>> - add new patch to propagate errors in mpam_reprogram_ris_partid() >>> - prevent loop when mpam_diable() tries MSC accesses again >>> - register MMIO error IRQ handler without IRQF_ONESHOT >>> - re-use existing "err" variable instead of declaring "ret" >>> - initialise mon_sel_lock later, to wait for interface decision >>> - convert timeout units for nominal latency, between us and ms >> >> [...] >> >>> >>> Andre Przywara (11): >>>    arm_mpam: let low level MSC accessors return an error >>>    arm_mpam: propagate MSC access errors for hw_probe functions >>>    arm_mpam: propagate MSC access errors for MBWU counters >>>    arm_mpam: propagate MSC access errors for msmon helpers >>>    arm_mpam: propagate MSC access errors for __ris_msmon_read() >>>    arm_mpam: propagate MSC access errors for state saving function >>>    arm_mpam: propagate MSC access errors for mpam_reprogram_ris_partid() >>>    arm_mpam: prepare mon_sel locking for MPAM-Fb >>>    arm_mpam: add MPAM-Fb MSC firmware access support >>>    arm_mpam: change MPAM-Fb error IRQ to use a threaded IRQ handler >>>    arm_mpam: detect and enable MPAM-Fb PCC support >>> >>>   drivers/resctrl/Makefile        |   2 +- >>>   drivers/resctrl/mpam_devices.c  | 820 +++++++++++++++++++++++--------- >>>   drivers/resctrl/mpam_fb.c       | 250 ++++++++++ >>>   drivers/resctrl/mpam_internal.h |  62 ++- >>>   include/linux/arm_mpam.h        |   2 +- >>>   5 files changed, 915 insertions(+), 221 deletions(-) >>>   create mode 100644 drivers/resctrl/mpam_fb.c >>> >> >> With this series (manually) applied to v7.2.rc6, the tests for the existing functions >> like kunit-tests, L3 cache partitioning, MBW (soft) limiting, llc_occupancy monitor >> look fine on NVidia's grace-hopper machine. > > Awesome, many thanks for doing that! > Glad to give it a try :-) >> Tested-by: Gavin Shan > > I'd assume this is a regression test, as your machine uses the standard MMIO interface? > If you don't mind, I'd put this tag on the first refactoring patches, so 01/11 - 08/11, and leave out the remaining 3, as they are about MPAM-Fb, which wasn't really tested, I guess? Also patch 10/11 (the error IRQ changes) changed, so I would drop all tags from this anyway. > Yes, it's a regression test. My Tested-by tag are only applied to 01/11 - 08/11. I don't have a machine where MPAM-fb is available to test 09/11 - 11/11. Thanks, Gavin > Cheers, > Andre >