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 D05222D8773; Thu, 9 Jul 2026 09:25:58 +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=1783589160; cv=none; b=fk9AsQY3d9H37ZU7vaipvfNHxNcHtSdz3B9Mpb+7WefRyYt+JBH/1/8fMMt6pnFrVppxEKRH+1Upo9AkU0y6thudJGh2wskKwoqSgH1RBGqzrNGJGD3a4EK6qcSZKVNhVmqyXZfMxwSUKmoG06o95922JQutCe23zIj3JvOxr8s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783589160; c=relaxed/simple; bh=r1QShwB/9V/I0bdqwOV4mWuyphrL3DCBdCUyGIHA03s=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ec968/s8qL+jwNap6WXStqLSlU3YP9EY/iCe/nKS3YLfbc+4Wxn/CDwaj76Y0el49jkfjIFnglpKkgtvoNxRiiXWD2ckkFD0GkRO2qSqQ9UL0zZMJCg3p8/quIBuuGCFv3040wPiOHHgWj6mkFFPTa2sTKWywGoNQHTMUIMoaDw= 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=soghxfur; 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="soghxfur" 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 E42F9357B; Thu, 9 Jul 2026 02:25:53 -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 57F2A3F66F; Thu, 9 Jul 2026 02:25:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783589158; bh=r1QShwB/9V/I0bdqwOV4mWuyphrL3DCBdCUyGIHA03s=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=soghxfurEEX84ljf4uRd93H+Thd3S0QZKTyNgrf/Ga7kG0mU7NGwTqf5c5fm7BGmg ssRgcMOUX3GkElbF48HVNBWA7lbZD2IhMGp/DpGGXtU+Uq57HwQr8MPEgUzoiNJLu7 fDDtZKikUufCT/CUuIZD8Kr9mEAwoj3rR4YNMHKM= Message-ID: <0aa3bbbc-c0f0-404c-b03b-9113a1e91ce5@arm.com> Date: Thu, 9 Jul 2026 10:25:54 +0100 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH v4 2/3] arm_mpam: resctrl: Add pass-through resctrl_arch_preconvert_bw() To: Reinette Chatre Cc: james.morse@arm.com, fenghuay@nvidia.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, corbet@lwn.net, x86@kernel.org, linux-doc@vger.kernel.org, dave.martin@arm.com References: <20260706160639.2136674-1-ben.horgan@arm.com> <20260706160639.2136674-3-ben.horgan@arm.com> <4c520a28-9a72-4abd-8e5b-654a312c92fd@intel.com> <8d5d9c98-54df-44fe-8795-189554ea2399@intel.com> Content-Language: en-US From: Ben Horgan In-Reply-To: <8d5d9c98-54df-44fe-8795-189554ea2399@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Reinette, On 7/7/26 15:51, Reinette Chatre wrote: > Hi Ben, > > On 7/7/26 1:35 AM, Ben Horgan wrote: >> Hi Reinette, >> >> On 7/6/26 22:33, Reinette Chatre wrote: >>> Hi Ben, >>> >>> On 7/6/26 9:06 AM, Ben Horgan wrote: >>>> resctrl rounds up the percentage value of the MBA based on the bw_gran. As >>>> MPAM uses a binary fixed point fraction format for MBA rather than a >>>> decimal percentage, this introduces rounding errors. >>>> >>>> Without this additional rounding, if the user reads the value in an MB >>>> schema and then writes it back to the schema, the value in hardware won't >>>> change. However, with this additional rounding, this guarantee is broken >>>> for systems with mbw_wd < 7. >>>> >>>> resctrl is introducing resctrl_arch_preconvert_bw() to allow the arch code >>>> to specify the conversion resctrl does to the user-provided bandwidth >>>> value. Add the MPAM version of resctrl_arch_preconvert_bw(). This does no >>>> conversion. >>>> >>>> Signed-off-by: Ben Horgan >>>> Reviewed-by: Reinette Chatre >>>> >>> >>> Unfortunately the "---" separator is missing here. >> >> Another silly mistake.. sorry about that. I've corrected locally and >> will send a respin in a day or two. > No problem. > > When you respin, could you please add a snippet to the cover about expectations > how this series should be merged? This will be the first piece of work that > touches the x86 and Arm driver as well as resctrl fs code. So far I assumed it > will go in via tip but I think it will help to state this from Arm side. Yes, I was assuming that too. I'll make it explicit in the cover letter. > We still need a plan for if/when the Arm side touches the same code though. Thankfully > this work is small. I'm open to whatever works best for you and the others involved. Thanks, Ben > > Reinette