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 F1FFB220687; Mon, 29 Sep 2025 17:44:42 +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=1759167884; cv=none; b=SNOn3ns6fVXP7Khh3PrQbpE2aQFTzwUDUcwOkTehoFlJ9B2JbXkbj3aJHXuTAjZPQfr2hV6AnJJdBP2PvB0OVLGMUnapbiA3Qa+u4bWvj7cdwQfeN0KJUeJ7tlEUR1o+8mLzHLavOTuwX/vS/n2vHjC14qvY7LEXfHSaON+sszE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759167884; c=relaxed/simple; bh=rtc9wYYiql/zxa6Fl+MwsGqtAZBHcTXLvHbZteu4+jE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HylyiBv67YMCS0Iu4nOAwYxzt2ieZxs3Gwc8pY9cER6ZSaM8/joX7n6HmG4WF5lBxhhy698eWgHoLLZMSCuYnW3Yb6IRkUACThV3a2cqOIiL/WqKjGoQJIsS8ERPGM2Y+pv5sN4+cw5wdWGJ5KE+bhUtL8HQr/jKlQn93JQtFQ8= 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 0F47C150C; Mon, 29 Sep 2025 10:44:34 -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 B1C543F59E; Mon, 29 Sep 2025 10:44:36 -0700 (PDT) Message-ID: <628b42e2-6605-4f19-8ee8-e1c8707a6f96@arm.com> Date: Mon, 29 Sep 2025 18:44:35 +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 11/29] arm_mpam: Probe hardware to find the supported partid/pmg values To: Jonathan Cameron Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org, 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, Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-12-james.morse@arm.com> <20250911161850.00005667@huawei.com> Content-Language: en-GB From: James Morse In-Reply-To: <20250911161850.00005667@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/09/2025 16:18, Jonathan Cameron wrote: > On Wed, 10 Sep 2025 20:42:51 +0000 > James Morse wrote: > >> CPUs can generate traffic with a range of PARTID and PMG values, >> but each MSC may also have its own maximum size for these fields. >> Before MPAM can be used, the driver needs to probe each RIS on >> each MSC, to find the system-wide smallest value that can be used. >> The limits from requestors (e.g. CPUs) also need taking into account. >> >> While doing this, RIS entries that firmware didn't describe are created >> under MPAM_CLASS_UNKNOWN. >> >> While we're here, implement the mpam_register_requestor() call >> for the arch code to register the CPU limits. Future callers of this >> will tell us about the SMMU and ITS. >> >> Signed-off-by: James Morse > Trivial stuff inline. > Reviewed-by: Jonathan Cameron Thanks! >> drivers/resctrl/mpam_devices.c | 150 +++++++++++++++++++++++++++++++- >> drivers/resctrl/mpam_internal.h | 6 ++ >> include/linux/arm_mpam.h | 14 +++ >> 3 files changed, 169 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c >> index c265376d936b..24dc81c15ec8 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c > > >> +int mpam_register_requestor(u16 partid_max, u8 pmg_max) >> +{ >> + int err = 0; >> + >> + spin_lock(&partid_max_lock); > guard() perhaps so you can return early in the error pat and avoid > need for local variable err. Negh ... okay. I dislike the guard thing as its never clear when the lock is unlocked. I'm not a fan of spooky action at a distance! >> + if (!partid_max_init) { >> + mpam_partid_max = partid_max; >> + mpam_pmg_max = pmg_max; >> + partid_max_init = true; >> + } else if (!partid_max_published) { >> + mpam_partid_max = min(mpam_partid_max, partid_max); >> + mpam_pmg_max = min(mpam_pmg_max, pmg_max); >> + } else { >> + /* New requestors can't lower the values */ >> + if (partid_max < mpam_partid_max || pmg_max < mpam_pmg_max) >> + err = -EBUSY; >> + } >> + spin_unlock(&partid_max_lock); >> + >> + return err; >> +} >> +EXPORT_SYMBOL(mpam_register_requestor); > >> @@ -470,9 +547,37 @@ int mpam_ris_create(struct mpam_msc *msc, u8 ris_idx, >> +static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc *msc, >> + u8 ris_idx) >> +{ >> + int err; >> + struct mpam_msc_ris *ris, *found = ERR_PTR(-ENOENT); >> + >> + lockdep_assert_held(&mpam_list_lock); >> + >> + if (!test_bit(ris_idx, &msc->ris_idxs)) { >> + err = mpam_ris_create_locked(msc, ris_idx, MPAM_CLASS_UNKNOWN, >> + 0, 0); >> + if (err) >> + return ERR_PTR(err); >> + } >> + >> + list_for_each_entry(ris, &msc->ris, msc_list) { >> + if (ris->ris_idx == ris_idx) { >> + found = ris; > I'd return ris; > > Then can do return ERR_PTR(-ENOENT) below and not bother with found. > > Ignore if this gets more complex later. Thank - this is another relic of more complex locking... Fixed as you suggested. >> + break; >> + } >> + } >> + >> + return found; >> +} > >> @@ -675,9 +813,18 @@ static struct platform_driver mpam_msc_driver = { >> >> static void mpam_enable_once(void) >> { >> + /* >> + * Once the cpuhp callbacks have been changed, mpam_partid_max can no >> + * longer change. >> + */ >> + spin_lock(&partid_max_lock); >> + partid_max_published = true; >> + spin_unlock(&partid_max_lock); >> + >> mpam_register_cpuhp_callbacks(mpam_cpu_online, mpam_cpu_offline); >> >> - pr_info("MPAM enabled\n"); >> + printk(KERN_INFO "MPAM enabled with %u PARTIDs and %u PMGs\n", >> + mpam_partid_max + 1, mpam_pmg_max + 1); > Not sure why pr_info before and printk now. That looks like a conflict gone wrong! Fixed. Thanks, James