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 CFFE22BE03D; Wed, 12 Nov 2025 15:33:04 +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=1762961588; cv=none; b=C84un0nlXY5XMSiAByfB0lJV6D/SiMAzoe97LPErrmVkgrzvJW58b/4Oy/anZLN1TOwiIkemu9aLiOoQ41cgNMX66Y9HBu0Tbc3X0TCL0aUt+M69cN49mNs2NIqFOEz3DNEoOIdKFD1YlennsXcGRVFosJveAqu5lmtqnQivR2k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762961588; c=relaxed/simple; bh=hJG4mORyBX4EkyEoNAxykxgfA/y6DRF79lt33YV3ch4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VwSyt3H9RFSNjOdcEInpzIsfzVwZjVDa+r2KjSGFqkOJe7ZNCtLfQpNcGchuZxFFt9Sppwq8WdOEPEQ8rHUqZ6TbjKBMgENxXEmiMVUIZFoigcEpTv8bSy76A0Mp7iIwJfM1yHLOflTMGpPERyxvAGOpuMR2Dwg5i84uvbelilM= 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 4B0681515; Wed, 12 Nov 2025 07:32:56 -0800 (PST) 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 261973F66E; Wed, 12 Nov 2025 07:32:59 -0800 (PST) Message-ID: <85ce2f10-d174-472d-b74c-a3e34dc4a40f@arm.com> Date: Wed, 12 Nov 2025 15:32:57 +0000 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 10/33] arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate To: Gavin Shan , james.morse@arm.com Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, bobo.shaobowang@huawei.com, carl@os.amperecomputing.com, catalin.marinas@arm.com, dakr@kernel.org, dave.martin@arm.com, david@redhat.com, dfustini@baylibre.com, fenghuay@nvidia.com, gregkh@linuxfoundation.org, guohanjun@huawei.com, jeremy.linton@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, lpieralisi@kernel.org, peternewman@google.com, quic_jiles@quicinc.com, rafael@kernel.org, robh@kernel.org, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, sudeep.holla@arm.com, tan.shaopeng@fujitsu.com, will@kernel.org, xhao@linux.alibaba.com, Shaopeng Tan References: <20251107123450.664001-1-ben.horgan@arm.com> <20251107123450.664001-11-ben.horgan@arm.com> <5b9136d6-b6c0-4f24-a8d2-05d7700140a8@redhat.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <5b9136d6-b6c0-4f24-a8d2-05d7700140a8@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Gavin, On 11/8/25 09:28, Gavin Shan wrote: > Hi Ben, > > On 11/7/25 10:34 PM, Ben Horgan wrote: >> From: James Morse >> >> Probing MPAM is convoluted. MSCs that are integrated with a CPU may >> only be accessible from those CPUs, and they may not be online. >> Touching the hardware early is pointless as MPAM can't be used until >> the system-wide common values for num_partid and num_pmg have been >> discovered. >> > > I'm not sure if below commit log is more clearer as I'm not a English > native speaker: Thanks for the detailed review of the messages and comments. I've skipped the ones that I think don't improve the clarity. (I see Jonathan has a detailed reply which matches my understanding of English.) > > MPAM probing is convoluted. MSCs that are integrated to a set of CPUs > may only be accessible from those CPUs, ... > >> Start with driver probe/remove and mapping the MSC. >> >> CC: Carl Worth >> Tested-by: Fenghua Yu >> Tested-by: Shaopeng Tan >> Tested-by: Peter Newman >> Signed-off-by: James Morse >> Signed-off-by: Ben Horgan >> --- >> Changes since v3: >>  From Jonathan: >> Include cleanup >> Use devm_mutex_init() >> Add an ERR_CAST() >> Fenghua: >> Return zero from update_msc_accessibility() >> Additional: >> Fail probe if MSC doesn't have an MMIO interface >> --- >>   arch/arm64/Kconfig              |   1 + >>   drivers/Kconfig                 |   2 + >>   drivers/Makefile                |   1 + >>   drivers/resctrl/Kconfig         |  15 +++ >>   drivers/resctrl/Makefile        |   4 + >>   drivers/resctrl/mpam_devices.c  | 194 ++++++++++++++++++++++++++++++++ >>   drivers/resctrl/mpam_internal.h |  49 ++++++++ >>   7 files changed, 266 insertions(+) >>   create mode 100644 drivers/resctrl/Kconfig >>   create mode 100644 drivers/resctrl/Makefile >>   create mode 100644 drivers/resctrl/mpam_devices.c >>   create mode 100644 drivers/resctrl/mpam_internal.h >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index c5e66d5d72cd..004d58cfbff8 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -2025,6 +2025,7 @@ config ARM64_TLB_RANGE >>     config ARM64_MPAM >>       bool "Enable support for MPAM" >> +    select ARM64_MPAM_DRIVER if EXPERT    # does nothing yet >>       select ACPI_MPAM if ACPI >>       help >>         Memory System Resource Partitioning and Monitoring (MPAM) is an >> diff --git a/drivers/Kconfig b/drivers/Kconfig >> index 4915a63866b0..3054b50a2f4c 100644 >> --- a/drivers/Kconfig >> +++ b/drivers/Kconfig >> @@ -251,4 +251,6 @@ source "drivers/hte/Kconfig" >>     source "drivers/cdx/Kconfig" >>   +source "drivers/resctrl/Kconfig" >> + >>   endmenu >> diff --git a/drivers/Makefile b/drivers/Makefile >> index 8e1ffa4358d5..20eb17596b89 100644 >> --- a/drivers/Makefile >> +++ b/drivers/Makefile >> @@ -194,6 +194,7 @@ obj-$(CONFIG_HTE)        += hte/ >>   obj-$(CONFIG_DRM_ACCEL)        += accel/ >>   obj-$(CONFIG_CDX_BUS)        += cdx/ >>   obj-$(CONFIG_DPLL)        += dpll/ >> +obj-y                += resctrl/ >>     obj-$(CONFIG_DIBS)        += dibs/ >>   obj-$(CONFIG_S390)        += s390/ >> diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig >> new file mode 100644 >> index 000000000000..ef2f3adf64a9 >> --- /dev/null >> +++ b/drivers/resctrl/Kconfig >> @@ -0,0 +1,15 @@ >> +menuconfig ARM64_MPAM_DRIVER >> +    bool "MPAM driver" >> +    depends on ARM64 && ARM64_MPAM && EXPERT >> +    help >> +      Memory System Resource Partitioning and Monitoring (MPAM) >> driver for >> +      System IP, e,g. caches and memory controllers. >> + >> +if ARM64_MPAM_DRIVER >> + >> +config ARM64_MPAM_DRIVER_DEBUG >> +    bool "Enable debug messages from the MPAM driver" >> +    help >> +      Say yes here to enable debug messages from the MPAM driver. >> + >> +endif > > I am asking myself why "depends on ARM64_MPAM_DRIVER" can't be used > here? :-) > >> diff --git a/drivers/resctrl/Makefile b/drivers/resctrl/Makefile >> new file mode 100644 >> index 000000000000..898199dcf80d >> --- /dev/null >> +++ b/drivers/resctrl/Makefile >> @@ -0,0 +1,4 @@ >> +obj-$(CONFIG_ARM64_MPAM_DRIVER)            += mpam.o >> +mpam-y                        += mpam_devices.o >> + >> +ccflags-$(CONFIG_ARM64_MPAM_DRIVER_DEBUG)    += -DDEBUG >> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/ >> mpam_devices.c >> new file mode 100644 >> index 000000000000..6c6be133d73a >> --- /dev/null >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -0,0 +1,194 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +// Copyright (C) 2025 Arm Ltd. >> + >> +#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +#include "mpam_internal.h" >> + >> +/* >> + * mpam_list_lock protects the SRCU lists when writing. Once the >> + * mpam_enabled key is enabled these lists are read-only, >> + * unless the error interrupt disables the driver. >> + */ > > s/when writing/for writing > s/are read-only/become read-only > >> +static DEFINE_MUTEX(mpam_list_lock); >> +static LIST_HEAD(mpam_all_msc); >> + >> +struct srcu_struct mpam_srcu; >> + >> +/* >> + * Number of MSCs that have been probed. Once all MSC have been >> probed MPAM >> + * can be enabled. >> + */ > > s/all MSC/all MSCs  (?) Changed. > >> +static atomic_t mpam_num_msc; >> + >> +/* >> + * An MSC can control traffic from a set of CPUs, but may only be >> accessible >> + * from a (hopefully wider) set of CPUs. The common reason for this >> is power >> + * management. If all the CPUs in a cluster are in PSCI:CPU_SUSPEND, the >> + * corresponding cache may also be powered off. By making accesses from >> + * one of those CPUs, we ensure this isn't the case. >> + */ > > s/An MSC/A MSC (?) > s/from a/from the > s/isn't the case/is the case (?) Updated this last one to be: By making accesses from one of those CPUs, we ensure we don't access a cache that's powered off. > >> +static int update_msc_accessibility(struct mpam_msc *msc) >> +{ >> +    u32 affinity_id; >> +    int err; >> + >> +    err = device_property_read_u32(&msc->pdev->dev, "cpu_affinity", >> +                       &affinity_id); >> +    if (err) >> +        cpumask_copy(&msc->accessibility, cpu_possible_mask); >> +    else >> +        acpi_pptt_get_cpus_from_container(affinity_id, >> +                          &msc->accessibility); >> +    return 0; >> +} >> + > > {} is needed for the block spanning multiple lines. Made it one line. > > I would validate msc->accessibility here instead of its caller > (do_mpam_msc_drv_probe()). > >         if (cpumask_empty(&msc->accessibility)) >             return {-EINVAL, -ENOENT}; > >> +static int fw_num_msc; >> + >> +static void mpam_msc_destroy(struct mpam_msc *msc) >> +{ >> +    struct platform_device *pdev = msc->pdev; >> + >> +    lockdep_assert_held(&mpam_list_lock); >> + >> +    list_del_rcu(&msc->all_msc_list); >> +    platform_set_drvdata(pdev, NULL); >> +} >> + >> +static void mpam_msc_drv_remove(struct platform_device *pdev) >> +{ >> +    struct mpam_msc *msc = platform_get_drvdata(pdev); >> + >> +    if (!msc) >> +        return; > > 'msc' is unlikely to be NULL here, so the check could be droped. Dropped. > >> + >> +    mutex_lock(&mpam_list_lock); >> +    mpam_msc_destroy(msc); >> +    mutex_unlock(&mpam_list_lock); >> + >> +    synchronize_srcu(&mpam_srcu); >> +} >> + >> +static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device >> *pdev) >> +{ >> +    int err; >> +    u32 tmp; >> +    struct mpam_msc *msc; >> +    struct resource *msc_res; >> +    struct device *dev = &pdev->dev; >> + >> +    lockdep_assert_held(&mpam_list_lock); >> + >> +    msc = devm_kzalloc(&pdev->dev, sizeof(*msc), GFP_KERNEL); >> +    if (!msc) >> +        return ERR_PTR(-ENOMEM); >> + >> +    err = devm_mutex_init(dev, &msc->probe_lock); >> +    if (err) >> +        return ERR_PTR(err); >> +    err = devm_mutex_init(dev, &msc->part_sel_lock); >> +    if (err) >> +        return ERR_PTR(err); >> +    msc->id = pdev->id; >> +    msc->pdev = pdev; >> +    INIT_LIST_HEAD_RCU(&msc->all_msc_list); >> +    INIT_LIST_HEAD_RCU(&msc->ris); >> + >> +    err = update_msc_accessibility(msc); >> +    if (err) >> +        return ERR_PTR(err); >> +    if (cpumask_empty(&msc->accessibility)) { >> +        dev_err_once(dev, "MSC is not accessible from any CPU!"); >> +        return ERR_PTR(-EINVAL); >> +    } >> + > > As suggested above, this check would be done inside > update_msc_accessibility(). Unless you object I'll keep this as is and make void update_msc_accessibility() a void function. I think this works better with the naming. > >> +    if (device_property_read_u32(&pdev->dev, "pcc-channel", &tmp)) >> +        msc->iface = MPAM_IFACE_MMIO; >> +    else >> +        msc->iface = MPAM_IFACE_PCC; >> + >> +    if (msc->iface == MPAM_IFACE_MMIO) { >> +        void __iomem *io; >> + >> +        io = devm_platform_get_and_ioremap_resource(pdev, 0, >> +                                &msc_res); >> +        if (IS_ERR(io)) { >> +            dev_err_once(dev, "Failed to map MSC base address\n"); >> +            return ERR_CAST(io); >> +        } >> +        msc->mapped_hwpage_sz = msc_res->end - msc_res->start; >> +        msc->mapped_hwpage = io; >> +    } else { >> +        return ERR_PTR(-ENOENT); > > Would be: >         return ERR_PTR(-EINVAL); Sure. > >> +    } >> + >> +    list_add_rcu(&msc->all_msc_list, &mpam_all_msc); >> +    platform_set_drvdata(pdev, msc); >> + >> +    return msc; >> +} >> + >> +static int mpam_msc_drv_probe(struct platform_device *pdev) >> +{ >> +    int err; >> +    struct mpam_msc *msc = NULL; >> +    void *plat_data = pdev->dev.platform_data; >> + >> +    mutex_lock(&mpam_list_lock); >> +    msc = do_mpam_msc_drv_probe(pdev); >> +    mutex_unlock(&mpam_list_lock); >> +    if (!IS_ERR(msc)) { >> +        /* Create RIS entries described by firmware */ >> +        err = acpi_mpam_parse_resources(msc, plat_data); >> +        if (err) >> +            mpam_msc_drv_remove(pdev); >> +    } else { >> +        err = PTR_ERR(msc); >> +    } >> + >> +    if (!err && atomic_add_return(1, &mpam_num_msc) == fw_num_msc) >> +        pr_info("Discovered all MSC\n"); > > s/all MSC/all MSCs > >> + >> +    return err; >> +} >> + >> +static struct platform_driver mpam_msc_driver = { >> +    .driver = { >> +        .name = "mpam_msc", >> +    }, >> +    .probe = mpam_msc_drv_probe, >> +    .remove = mpam_msc_drv_remove, >> +}; >> + >> +static int __init mpam_msc_driver_init(void) >> +{ >> +    if (!system_supports_mpam()) >> +        return -EOPNOTSUPP; >> + >> +    init_srcu_struct(&mpam_srcu); >> + >> +    fw_num_msc = acpi_mpam_count_msc(); >> + >> +    if (fw_num_msc <= 0) { >> +        pr_err("No MSC devices found in firmware\n"); >> +        return -EINVAL; >> +    } >> + >> +    return platform_driver_register(&mpam_msc_driver); >> +} >> +subsys_initcall(mpam_msc_driver_init); >> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/ >> mpam_internal.h >> new file mode 100644 >> index 000000000000..540066903eca >> --- /dev/null >> +++ b/drivers/resctrl/mpam_internal.h >> @@ -0,0 +1,49 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +// Copyright (C) 2025 Arm Ltd. >> + >> +#ifndef MPAM_INTERNAL_H >> +#define MPAM_INTERNAL_H >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +struct platform_device; >> + >> +struct mpam_msc { >> +    /* member of mpam_all_msc */ >> +    struct list_head    all_msc_list; >> + >> +    int            id; >> +    struct platform_device    *pdev; >> + >> +    /* Not modified after mpam_is_enabled() becomes true */ >> +    enum mpam_msc_iface    iface; >> +    u32            nrdy_usec; >> +    cpumask_t        accessibility; >> + >> +    /* >> +     * probe_lock is only taken during discovery. After discovery these >> +     * properties become read-only and the lists are protected by SRCU. >> +     */ >> +    struct mutex        probe_lock; >> +    unsigned long        ris_idxs; >> +    u32            ris_max; >> + >> +    /* mpam_msc_ris of this component */ >> +    struct list_head    ris; >> + >> +    /* >> +     * part_sel_lock protects access to the MSC hardware registers >> that are >> +     * affected by MPAMCFG_PART_SEL. (including the ID registers that >> vary >> +     * by RIS). >> +     * If needed, take msc->probe_lock first. >> +     */ >> +    struct mutex        part_sel_lock; >> + >> +    void __iomem        *mapped_hwpage; >> +    size_t            mapped_hwpage_sz; >> +}; >> +#endif /* MPAM_INTERNAL_H */ > > Thanks, > Gavin > Thanks, Ben