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 025CE2BEC45; Mon, 9 Feb 2026 10:04:08 +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=1770631449; cv=none; b=RTJmMOWvYpCVU0RDat5zDDMTGd5uhOvyxdafQkIPEB56VzH7h5EAr2h1XXPwmzKH7UQmjqt1mCzJEZGFUdkqhzAVg3QbvKKR/jY6nBCr58xT3R1eacG5qej0GvjFz8D8hK37cDRFYq1QJi5ziwgTJZciTKLuFcAJ2dxV70JAHa0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770631449; c=relaxed/simple; bh=N38vbDeMMBRSF9rOlC/b2KTnP4Nk87rzrATIvwEGPWM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=L1FziAgisD6T2mHLPtnE3lmK6Mvf+gmXJ4N0S6bUZTAShDEpkGa4Fns4HHO6l1iFIkKOklXrXMMnPeI4pp5i6BzmUqb6jlgvbaGd/bUnuSPIEig7ChKQH5nOG83K9SpVJYYX4VjX+KaGM8un97r0y0vRX1BtK5Nnpo1s0o0MsG4= 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 055A3339; Mon, 9 Feb 2026 02:04:02 -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 480D03F632; Mon, 9 Feb 2026 02:04:03 -0800 (PST) Message-ID: <9a8a163e-887a-45fc-aae5-45e564360c8b@arm.com> Date: Mon, 9 Feb 2026 10:04:01 +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 v4 00/41] arm_mpam: Add KVM/arm64 and resctrl glue code To: "Shaopeng Tan (Fujitsu)" 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" , "jonathan.cameron@huawei.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" , "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" , "zengheng4@huawei.com" , "linux-doc@vger.kernel.org" References: <20260203214342.584712-1-ben.horgan@arm.com> From: Ben Horgan Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Shaopeng, On 2/9/26 08:25, Shaopeng Tan (Fujitsu) wrote: > Hello Ben, > >> This new version of the mpam missing pieces series has a few significant >> changes in the mpam driver part of the series. The heuristics for deciding >> if features should be exposed are tightened. This is to fix some >> inaccuracies and avoid overcommitting before needed - shout if this changes >> anything on your platform. The final patch adds documentation which >> explains which features you should expect. The ABMC emulation is dropped >> for the moment as it requires resctrl changes to support for MPAM without >> breaking the abi. The default 5% gap for min_bw is dropped in favour of a >> simple default (kept for grace). The series is based on x86/resctrl [1] as >> resctrl has telemetry patches queued which change the arch interface. > > Could you please elaborate on why fs/resctrl changes are required to support only the counter assignment part of ABMC? > Currently, many SoC chips have an insufficient number of memory bandwidth monitors. Sure. When the counter assignment mode is 'mbm_event; resctrl assumes the mbm events are configurable. The 'event_filter' files at info/L3_MON/event_configs//event_filter are used to display and set this configuration. In MPAM event configuration is not supported and so showing a read/writable 'event_filter' file is misleading to the user and needs to be hidden for MPAM support. Just to give you a flavour of the change, here's a hack to show the correct thing for MPAM: --- a/fs/resctrl/rdtgroup.c +++ b/fs/resctrl/rdtgroup.c @@ -2338,6 +2338,9 @@ static int resctrl_mkdir_event_configs(struct rdt_resource *r, struct kernfs_nod if (ret) goto out; + if (!resctrl_arch_is_evt_configurable(mevt->evtid)) + continue; + > We would be grateful if you could support the counter assignment part of ABMC. It is not a big change in resctrl but I thought it best to not gate the rest of this series on an additional change in another subsystem. I am current looking into this and hope to get the patches on the list early in the next cycle. > > Best regards, > Shaopeng TAN > > Thanks, Ben