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 95AA0280329; Tue, 11 Nov 2025 17:45:42 +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=1762883144; cv=none; b=WD5mirH8H08dG/VFaP8l900s04vD6wtNdgcViZZWbI6BKGycBnNZP3LrggUGWFXJjsLNFB4zdxIG6kdZPv+hLLsXG9bRyGPV0lkoQp1wMDb2keVntE8B+duCeoLwQIwUFpwqGehy1MOtPL/rOiX1wPDakJ5IMUMsOKdJKIH/Wrg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762883144; c=relaxed/simple; bh=337GK2VBuQER80HrR8VLp/BBTkzZ42YWnJrE1tKersU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hDZk8KF2coMx+goYTCndQbX7nWGTytJY6B6esO7A2zC79MNbU9/UBrbVwq2M4FQ3WHbp33yjukH8u31ZQPkefiDm3qtxi2RardWBOBzGA53WDGVUWMzycFhRPpG5hWC/7tqZstV9tt9/KqW+zo1h27Y76Z2Rcf0pnCLPGo6KIWU= 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 28353497; Tue, 11 Nov 2025 09:45:34 -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 4536B3F5A1; Tue, 11 Nov 2025 09:45:37 -0800 (PST) Message-ID: Date: Tue, 11 Nov 2025 17:45:35 +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 23/33] arm_mpam: Allow configuration to be applied and restored during cpu online To: Jonathan Cameron Cc: james.morse@arm.com, 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, gshan@redhat.com, guohanjun@huawei.com, jeremy.linton@arm.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 References: <20251107123450.664001-1-ben.horgan@arm.com> <20251107123450.664001-24-ben.horgan@arm.com> <20251110172724.00005675@huawei.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <20251110172724.00005675@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jonathan, On 11/10/25 17:27, Jonathan Cameron wrote: > On Fri, 7 Nov 2025 12:34:40 +0000 > Ben Horgan wrote: > >> From: James Morse >> >> When CPUs come online the MSC's original configuration should be restored. >> >> Add struct mpam_config to hold the configuration. This has a bitmap of >> features that were modified. Once the maximum partid is known, allocate > > I'm not following 'were modified'. When? Sometime in the past? > Perhaps "features that have been modified when XXX happens" or > > Having read the code I think this is something like "are modified as configuration > is read". > >> a configuration array for each component, and reprogram each RIS >> configuration from this. >> >> CC: Dave Martin >> Signed-off-by: James Morse >> Cc: Shaopeng Tan (Fujitsu) tan.shaopeng@fujitsu.com >> Cc: Peter Newman peternewman@google.com >> Signed-off-by: Ben Horgan >> --- >> Changes since v3: >> Drop tags >> Fix component reset, otherwise cpbm wrong and controls not set. >> Add a cfg_lock to guard configuration of an msc > > The use of bitmap_set() for things that aren't unsigned long (arrays) is a bad > idea. Much better to use GENMASK() to fill those. > >> --- >> drivers/resctrl/mpam_devices.c | 268 ++++++++++++++++++++++++++++++-- >> drivers/resctrl/mpam_internal.h | 27 ++++ >> 2 files changed, 280 insertions(+), 15 deletions(-) > Why manipulate a u32 with bitmap_set() with a horrible pretend it's an unsigned long cast. > Instead just do: > comp->cfg[i].cpbm = GENMASK(cprops->cpbm_wd, 0); > Which is indeed what bitmap_set will do internally due to an optimization for small bitmaps > but lets avoid that making one integer pretend to be another of a different length. > > >> + bitmap_set((unsigned long *)&comp->cfg[i].mbw_pbm, 0, cprops->mbw_pbm_bits); >> + bitmap_set((unsigned long *)&comp->cfg[i].mbw_max, 16 - cprops->bwa_wd, cprops->bwa_wd); >> + } >> +} > It is a bit nasty. I was trying to keep the concept of setting n bits and avoid considering explicitly what happens when n is zero. These bitmap_set() can become: if (cprops->cpbm_wd) comp->cfg[i].cpbm = GENMASK(cprops->cpbm_wd - 1, 0); if (cprops->mbw_pbm_bits) comp->cfg[i].mbw_pbm = GENMASK(cprops->mbw_pbm_bits - 1, 0); if (cprops->bwa_wd) comp->cfg[i].mbw_max = GENMASK(15, 16 - cprops->bwa_wd); Thanks, Ben