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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 E0AE9C282C6 for ; Thu, 24 Jan 2019 13:22:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCB4B218AE for ; Thu, 24 Jan 2019 13:22:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728084AbfAXNWy (ORCPT ); Thu, 24 Jan 2019 08:22:54 -0500 Received: from 8bytes.org ([81.169.241.247]:59588 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728031AbfAXNWy (ORCPT ); Thu, 24 Jan 2019 08:22:54 -0500 Received: by theia.8bytes.org (Postfix, from userid 1000) id 10E37389; Thu, 24 Jan 2019 14:22:51 +0100 (CET) Date: Thu, 24 Jan 2019 14:22:50 +0100 From: Joerg Roedel To: Lu Baolu Cc: David Woodhouse , ashok.raj@intel.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Liu Yi L , Jacob Pan Subject: Re: [PATCH 1/1] iommu/vt-d: Leave scalable mode default off Message-ID: <20190124132250.k3rnlpaqazmatzaf@8bytes.org> References: <20190124023132.20410-1-baolu.lu@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190124023132.20410-1-baolu.lu@linux.intel.com> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 24, 2019 at 10:31:32AM +0800, Lu Baolu wrote: > Commit 765b6a98c1de3 ("iommu/vt-d: Enumerate the scalable > mode capability") enables VT-d scalable mode if hardware > advertises the capability. As we will bring up different > features and use cases to upstream in different patch > series, it will leave some intermediate kernel versions > which support partial features. Hence, end user might run > into problems when they use such kernels on bare metals > or virtualization environments. I don't get it, can you be more specific about the problems that users might run into? And is this patch needed as a fix for v5.0 or is it just a precaution because future patches might break something for users? Regards, Joerg