From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F666C43331 for ; Mon, 11 Nov 2019 05:23:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11C1820856 for ; Mon, 11 Nov 2019 05:23:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726889AbfKKFXt (ORCPT ); Mon, 11 Nov 2019 00:23:49 -0500 Received: from mga03.intel.com ([134.134.136.65]:45254 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725796AbfKKFXs (ORCPT ); Mon, 11 Nov 2019 00:23:48 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Nov 2019 21:23:48 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,291,1569308400"; d="scan'208";a="228824039" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by fmsmga004.fm.intel.com with ESMTP; 10 Nov 2019 21:23:46 -0800 Cc: baolu.lu@linux.intel.com, Joerg Roedel , David Woodhouse , kevin.tian@intel.com, ashok.raj@intel.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jacob.jun.pan@intel.com Subject: Re: [PATCH v2 1/1] iommu/vt-d: Add Kconfig option to enable/disable scalable mode To: Qian Cai References: <20191109034039.27964-1-baolu.lu@linux.intel.com> <472617D4-1652-45FB-90A4-0D45766DB78B@lca.pw> From: Lu Baolu Message-ID: Date: Mon, 11 Nov 2019 13:20:52 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <472617D4-1652-45FB-90A4-0D45766DB78B@lca.pw> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 11/11/19 10:58 AM, Qian Cai wrote: > > >> On Nov 8, 2019, at 10:43 PM, Lu Baolu wrote: >> >> +config INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON >> + prompt "Enable Intel IOMMU scalable mode by default" >> + depends on INTEL_IOMMU >> + help >> + Selecting this option will enable the scalable mode if >> + hardware presents the capability. If this option is not >> + selected, scalable mode support could also be enabled >> + by passing intel_iommu=sm_on to the kernel. >> + > > Does it also make sense to mention which hardware presents this capability or how to check it? > The scalable mode is defined in VT-d 3.0. The scalable mode capability could be checked by reading /sys/devices/virtual/iommu/dmar*/intel- iommu/ecap. It's currently not friendly for reading. You need to decode it according to the spec. Best regards, baolu