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 E414A47ACDD for ; Tue, 13 Oct 2026 09:40:02 +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=1791884404; cv=none; b=ZksDrXOTCKSc91vgxsAxHJIoUq7+LhSLJ6dfPWDosa/g8KROf/FZ33/KvRQeEqUntbU2rP5+HUNFYohJRnaiAg5nsZ4hYJ5yN4xQQMAiphh53mRes4w1aP5ES/lKuC590bDDtWu5tKz8RzONwGEqLstILl5010Mx3X2r+5LIeA8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791884404; c=relaxed/simple; bh=XZTzCR3YxKwqm649NplBZ5ogv6xoQ0xU3FORRre3ZTg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eNFVd2ALRtFc6RLjASBsV9WUA7XRadI5pHKiwWV5ZK6ulbjT6UtFMt+1E7fh2RozrDbtXE58jRUnj/nigAIeHQjc5QZ4sLnQR4awx/+gc5kDrsCMAb13U/SkWDt+3xJiCglfRx0aTEB6fDk18EH+nZDyB9zlN9Vm8UUlaWhRbIA= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=nJyOJX4H; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="nJyOJX4H" 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 0368F169C; Tue, 13 Oct 2026 02:39:59 -0700 (PDT) Received: from [10.2.212.8] (e134344.arm.com [10.2.212.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9CE253F7B4; Tue, 13 Oct 2026 02:40:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1791884402; bh=XZTzCR3YxKwqm649NplBZ5ogv6xoQ0xU3FORRre3ZTg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=nJyOJX4H2K9Pa4BGjhnhpGbsn6lEr2zXS4gJ+55tCTfZ41HPL6Ltga7TA+iTNGPu4 Qy6/+gG3YZVWpe3GJ8goUL5zZK7nXacxuqAkM6689bebDTTO5mJCvLRqiUl9sE7sRT 3mFZyJ3R8gZfk4SZoj9fK2LAAKnSG/cpuOWwVpt0= Message-ID: <019fee57-8984-4bd6-8912-ec9b1718eb08@arm.com> Date: Tue, 13 Oct 2026 10:40:00 +0100 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 v5] arm_mpam: Use an atomic counter to schedule mpam_enable_once() To: Ping Li , james.morse@arm.com Cc: linux-kernel@vger.kernel.org, reinette.chatre@intel.com, fenghuay@nvidia.com References: <20260915115646.54113-1-leeonion.muyu@gmail.com> <20260921114957.3382350-1-leeonion.muyu@gmail.com> Content-Language: en-US From: Ben Horgan In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Ping, On 06/10/2026 07:31, Ping Li wrote: > Hi Ben, > Gentle ping on this patch. It would be good to know if there is > anything else you would like changed. > Thanks, > Ping > > Ping Li 于2026年9月21日周一 19:50写道： > >> mpam_discovery_cpu_online() scheduled mpam_enable() after each MSC >> probe, and mpam_enable() walked the whole MSC list taking each probe >> lock in turn to check if all the MSCs had been probed. >> >> Count the MSCs that have had their hardware probed with >> mpam_num_msc_probed, and schedule mpam_enable_once() directly when the >> count reaches fw_num_msc, the number of MSCs reported by firmware. >> MSCs that were already probed no longer cause work to be scheduled. >> >> Suggested-by: Ben Horgan >> Signed-off-by: Ping Li It's a bit late for 7.4 now but I should be able to take this next cycle. Reviewed-by: Ben Horgan Thanks, Ben >> --- >> Changes in v5: >> - Schedule mpam_broken_work at the error site and return early, >> removing the duplicate err check at the end of the function. >> >> drivers/resctrl/mpam_devices.c | 69 +++++++++++---------------------- >> drivers/resctrl/mpam_internal.h | 2 - >> 2 files changed, 22 insertions(+), 49 deletions(-) >> >> diff --git a/drivers/resctrl/mpam_devices.c >> b/drivers/resctrl/mpam_devices.c >> index 2f09f4b78bd3..4fc82acd854e 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -49,12 +49,20 @@ static LIST_HEAD(mpam_all_msc); >> >> struct srcu_struct mpam_srcu; >> >> +/* Number of MSCs reported by firmware */ >> +static int fw_num_msc; >> + >> /* >> * Number of MSCs that have been probed. Once all MSCs have been probed >> MPAM >> * can be enabled. >> */ >> static atomic_t mpam_num_msc; >> >> +/* Number of MSCs that have had their hardware probed */ >> +static atomic_t mpam_num_msc_probed; >> + >> +static void mpam_enable_once(struct work_struct *work); >> + >> static int mpam_cpuhp_state; >> static DEFINE_MUTEX(mpam_cpuhp_state_lock); >> >> @@ -72,7 +80,7 @@ static DEFINE_SPINLOCK(partid_max_lock); >> * scheduled via this work_struct. If access to an MSC depends on a CPU >> that >> * was not brought online at boot, this can happen surprisingly late. >> */ >> -static DECLARE_WORK(mpam_enable_work, &mpam_enable); >> +static DECLARE_WORK(mpam_enable_work, &mpam_enable_once); >> >> /* >> * All mpam error interrupts indicate a software bug. On receipt, disable >> the >> @@ -1854,7 +1862,6 @@ static int mpam_discovery_cpu_online(unsigned int >> cpu) >> { >> int err = 0; nit: don't need the ' = 0' anymore. >> struct mpam_msc *msc; >> - bool new_device_probed = false; >> >> if (mpam_is_enabled()) >> return 0; >> @@ -1865,24 +1872,22 @@ static int mpam_discovery_cpu_online(unsigned int >> cpu) >> if (!cpumask_test_cpu(cpu, &msc->accessibility)) >> continue; >> >> - mutex_lock(&msc->probe_lock); >> - if (!msc->probed) >> - err = mpam_msc_hw_probe(msc); >> - mutex_unlock(&msc->probe_lock); >> + guard(mutex)(&msc->probe_lock); >> + if (msc->probed) >> + continue; >> >> - if (err) >> - break; >> - new_device_probed = true; >> - } >> + err = mpam_msc_hw_probe(msc); >> + if (err) { >> + mpam_disable_reason = "error during probing"; >> + schedule_work(&mpam_broken_work); >> + return err; >> + } >> >> - if (new_device_probed && !err) >> - schedule_work(&mpam_enable_work); >> - if (err) { >> - mpam_disable_reason = "error during probing"; >> - schedule_work(&mpam_broken_work); >> + if (atomic_add_return(1, &mpam_num_msc_probed) == >> fw_num_msc) >> + schedule_work(&mpam_enable_work); >> } >> >> - return err; >> + return 0; >> } >> >> static int mpam_cpu_offline(unsigned int cpu) >> @@ -2106,8 +2111,6 @@ static struct mpam_msc *do_mpam_msc_drv_probe(struct >> platform_device *pdev) >> return msc; >> } >> >> -static int fw_num_msc; >> - >> static int mpam_msc_drv_probe(struct platform_device *pdev) >> { >> int err; >> @@ -2713,7 +2716,7 @@ static int mpam_allocate_config(void) >> return 0; >> } >> >> -static void mpam_enable_once(void) >> +static void mpam_enable_once(struct work_struct *work) >> { >> int err; >> >> @@ -2867,34 +2870,6 @@ void mpam_disable(struct work_struct *ignored) >> pr_err_once("MPAM disabled due to %s\n", mpam_disable_reason); >> } >> >> -/* >> - * Enable mpam once all devices have been probed. >> - * Scheduled by mpam_discovery_cpu_online() once all devices have been >> created. >> - * Also scheduled when new devices are probed when new CPUs come online. >> - */ >> -void mpam_enable(struct work_struct *work) >> -{ >> - static atomic_t once; >> - struct mpam_msc *msc; >> - bool all_devices_probed = true; >> - >> - /* Have we probed all the hw devices? */ >> - guard(srcu)(&mpam_srcu); >> - list_for_each_entry_srcu(msc, &mpam_all_msc, all_msc_list, >> - srcu_read_lock_held(&mpam_srcu)) { >> - mutex_lock(&msc->probe_lock); >> - if (!msc->probed) >> - all_devices_probed = false; >> - mutex_unlock(&msc->probe_lock); >> - >> - if (!all_devices_probed) >> - break; >> - } >> - >> - if (all_devices_probed && !atomic_fetch_inc(&once)) >> - mpam_enable_once(); >> -} >> - >> #define maybe_update_config(cfg, feature, newcfg, member, changes) do { \ >> if (mpam_has_feature(feature, newcfg) && \ >> (newcfg)->member != (cfg)->member) { \ >> diff --git a/drivers/resctrl/mpam_internal.h >> b/drivers/resctrl/mpam_internal.h >> index 04d1a59f02af..085f086e2b2d 100644 >> --- a/drivers/resctrl/mpam_internal.h >> +++ b/drivers/resctrl/mpam_internal.h >> @@ -452,8 +452,6 @@ extern struct list_head mpam_classes; >> extern u16 mpam_partid_max; >> extern u8 mpam_pmg_max; >> >> -/* Scheduled work callback to enable mpam once all MSC have been probed */ >> -void mpam_enable(struct work_struct *work); >> void mpam_disable(struct work_struct *work); >> >> /* Reset all the RIS in a class under cpus_read_lock() */ >> -- >> 2.34.1 >> >> >