From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE9292D738F; Wed, 14 Oct 2026 16:23:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791995020; cv=none; b=S4CB6rGgdax55+zlq1rSIMJgh3xLhTadU5jUj8DSni6ix9BPAlM5Q//+m7sUkRk83kh0YNmmxkfeI6/JW54lNQdX3ns3Ib4u79oYCUzKuVKNtu6IawbV2woQ2UAA0SYFDDygTVG0Jnv8cHcFCXb60ezkR1o2n8zoX5hYYyxPcJ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791995020; c=relaxed/simple; bh=Sc9czeDu67poAhucBNC67hnNdkGzJdjFqK99IfPlVnQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mUDJ2Krhfk2yRBiJvjcBzVW/iXMsKKm4vvaVfG1P3pocVXnIctawq5AnZzUULTorjw+J9nGZnNZUJmDvuWCRzDNmbtDks1/IFG6dx77SkWN1afs/zxY0g3UpXTJCN1/xovuuhNqHjIvqt0chi12GhQRCrArW6R/kg5K2Lx54rSQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=DPYeLOuO; arc=none smtp.client-ip=192.198.163.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="DPYeLOuO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1791995019; x=1823531019; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Sc9czeDu67poAhucBNC67hnNdkGzJdjFqK99IfPlVnQ=; b=DPYeLOuOau+PSOrew2YOx4FrmRtL8T4WRchUxbngYdwy2BCdeo8h/jv0 wKHDvx76Hu1XQgBQvSS//9Fp9uVo79IUUJioTR4vga11CtD9AKCNZ429F OsQB2ew4j1rM0fBi/a0W61p5uLNBl7UCX6SdpaPPJY1wYJWorCe61j9UV dUx+UuSJxzUZL1tWOVJ9S3o1bFpb9YfS/N/jTbiWdfGxMo2yE1zSPdRA5 tTwXkCBrPfoUr2Rw4Jyz/eDDIMILszKFhzRXzM8asRMci1D35VKxv2Z4z HmcY3GyOs95IbvG6bkM/jvPeG58Ll4sesUhTxYOTcgmFy5Op0+to9cQsS g==; X-CSE-ConnectionGUID: xFwDs0EwRmeuxXImTW1qVw== X-CSE-MsgGUID: YBbGGF2rSSu4+bQfOWGhfg== X-IronPort-AV: E=McAfee;i="6800,10657,11935"; a="645828" X-IronPort-AV: E=Sophos;i="6.27,158,1787036400"; d="scan'208";a="645828" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2026 09:23:38 -0700 X-CSE-ConnectionGUID: qD9SqOlsR8u4APPZCy6NIg== X-CSE-MsgGUID: pUXwMxsdRcO+OWpJ5Ztelw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,158,1787036400"; d="scan'208";a="1909041" Received: from gabaabhi-mobl2.amr.corp.intel.com (HELO [10.125.110.36]) ([10.125.110.36]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2026 09:23:37 -0700 Message-ID: <3466e889-82a0-41ac-9013-7d21020b5092@intel.com> Date: Wed, 14 Oct 2026 09:23:35 -0700 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: [RFC PATCH v2 0/3] cxl: Provide explicit RAM region creation for Type-2 providers To: "Lucero Palau, Alejandro" , Richard Cheng , jic23@kernel.org, dave@stgolabs.net, alison.schofield@intel.com, vishal.l.verma@intel.com, iweiny@kernel.org, ming.li@zohomail.com Cc: kaihengf@nvidia.com, kobak@nvidia.com, newtonl@nvidia.com, kristinc@nvidia.com, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261007090540.43817-1-icheng@nvidia.com> <1fd14fc6-de0d-4980-ac8b-8138dd5ef17c@amd.com> From: Dave Jiang Content-Language: en-US In-Reply-To: <1fd14fc6-de0d-4980-ac8b-8138dd5ef17c@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/14/26 8:34 AM, Lucero Palau, Alejandro wrote: > > On 07/10/2026 10:05, Richard Cheng wrote: >> A Type-2 provider uses devm_cxl_probe_mem() to register its memdev >> and obtain an HPA range. This requires an existing committed region, >> so registration fails when firmware has not configured one. >> >> Firmware may provide a suitable CFMWS window without programming a >> region. > > > Hi Richard, > > > FWIW, I unsuccessfully  tried to explain this possibility to "BIOS people". The fact is, nowadays for AMD and I think for Intel as well, if there is no CXL device detected with CXL.mem enabled, the BIOS will neither set HDMs  nor there will be a CFMWS. Hmmmm....don't they have to reserve CFMWS for hotplug? DJ > > > >> Hot-added devices can have the same requirement. A provider >> needs its endpoint topology established before deciding when to >> create a region and how much memory to map. > > > Another unsuccessfully discussion was to avoid BIOS setting HDMs at hotplug time as this could race with host dynamic regions creation. > > > I'm commenting these two things here for maybe having a community/kernel discussion with the goal of defining what BIOSes should do and mostly what they should not do if they want to be compatible with kernel expectations. > >