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 7673D3446D4 for ; Tue, 6 Jan 2026 15:23:12 +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=1767712994; cv=none; b=C0ZdoCap4qSa+uFraERaBo4duXJWISu1uzKmTYYW+IPy1qLOUZuAMFMq6FeNgb+r/E18qjMFqDrCjRNx0yJ+M+k6UAHHzGRg8DwCuoqoxhRBRwv01ayS4VAQD+nnoxOgyjSKMvqYNH6jFCEoLuVgVIJTJrtk6qFoIyr0wWAgxAk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767712994; c=relaxed/simple; bh=p5nUWO5+OlHwXmE9Nhvkfke+uGAizu12Xj/w8NHePzM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZS16/mHUH3c3RMAnLOMAiyloQAAV0neLF3lC6QHOFkpOj5abHsQ+efacdV8kXkcJs82p4KdFjjce7xfdEV21baiu/Q3U55TUnvu+nZw9sfO6o0eORgMxKcbYAMymGSSqe8hMPrAq3S8b+gUl7PtsUskUKKu0axdAosRhAknKpw8= 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 D4771497; Tue, 6 Jan 2026 07:23:04 -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 C79833F5A1; Tue, 6 Jan 2026 07:23:06 -0800 (PST) Message-ID: Date: Tue, 6 Jan 2026 15:23:05 +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 v2 23/45] arm_mpam: resctrl: Add rmid index helpers To: Jonathan Cameron Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, carl@os.amperecomputing.com, dave.martin@arm.com, david@kernel.org, dfustini@baylibre.com, fenghuay@nvidia.com, gshan@redhat.com, james.morse@arm.com, kobak@nvidia.com, lcherian@marvell.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peternewman@google.com, punit.agrawal@oss.qualcomm.com, quic_jiles@quicinc.com, reinette.chatre@intel.com, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, tan.shaopeng@fujitsu.com, xhao@linux.alibaba.com, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, kvmarm@lists.linux.dev References: <20251219181147.3404071-1-ben.horgan@arm.com> <20251219181147.3404071-24-ben.horgan@arm.com> <20260106112115.00000201@huawei.com> <316c5635-75af-4ebb-ad2c-fab0742beb20@arm.com> <20260106140447.0000602b@huawei.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <20260106140447.0000602b@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jonathan, On 1/6/26 14:04, Jonathan Cameron wrote: > On Tue, 6 Jan 2026 11:33:44 +0000 > Ben Horgan wrote: > >> Hi Jonathan, >> >> On 1/6/26 11:21, Jonathan Cameron wrote: >>> On Fri, 19 Dec 2025 18:11:25 +0000 >>> Ben Horgan wrote: >>> >>>> From: James Morse >>>> >>>> Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some >>>> data structures by index. This allows x86 to map indexes to RMID, and MPAM >>>> to map them to partid-and-pmg. >>>> >>>> Add the helpers to do this. >>>> >>>> Signed-off-by: James Morse >>>> Signed-off-by: Ben Horgan >>> one comment inline. >>> I messed around with GENMASK + field_prep()/field_get() - new >>> versions of these with no need for runtime constant masks, but >>> it ended up as not that much more readable than what you have here. >>> >>> Reviewed-by: Jonathan Cameron >>>> --- >>>> Changes since rfc: >>>> Use ~0U instead of ~0 in lhs of left shift >>>> --- >>>> drivers/resctrl/mpam_resctrl.c | 28 ++++++++++++++++++++++++++++ >>>> include/linux/arm_mpam.h | 3 +++ >>>> 2 files changed, 31 insertions(+) >>>> >>>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c >>>> index 4275b1a85887..bdbc5504964b 100644 >>>> --- a/drivers/resctrl/mpam_resctrl.c >>>> +++ b/drivers/resctrl/mpam_resctrl.c >>>> @@ -120,6 +120,34 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored) >>>> return mpam_partid_max + 1; >>>> } >>>> >>>> +u32 resctrl_arch_system_num_rmid_idx(void) >>>> +{ >>>> + u8 closid_shift = fls(mpam_pmg_max); >>>> + u32 num_partid = resctrl_arch_get_num_closid(NULL); >>>> + >>>> + return num_partid << closid_shift; >>> >>> Given I think you restrict mpam_pmg_max to be power of 2 elsewhere, >>> doesn't this end up the same as something like >>> return mpam_pmg_max * resctrl_arch_get_num_closid(NULL); >>> Maybe its worth keeping it in the form you have here as >>> it sort of provides documentation for how you pack those IDs >> >> We only warn if (mpam_pmg_max + 1) is a power of 2 and so I'll keep this >> as it is, although yours is equivalent in the expected case. > > Do the resulting 'holes' in the values that are valid here cause > trouble it isn't power of 2? Theoretically they are a problem, and if resctrl allocates them then we would get invalid pmg values which can cause msc error interrupts. However, I don't know of any platforms where pmg_max is more than 1. Anyhow, I'll look into using multiplication in these rmid arch helpers rather than just shifting to avoid leaving these holes. > >> >>> >>>> +} >>> >> >> Thanks, >> >> Ben >> >> > -- Thanks, Ben