Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759215AbdCVLXy (ORCPT ); Wed, 22 Mar 2017 07:23:54 -0400 Received: from mx2.suse.de ([195.135.220.15]:56139 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758838AbdCVLXs (ORCPT ); Wed, 22 Mar 2017 07:23:48 -0400 Date: Wed, 22 Mar 2017 11:49:00 +0100 From: Joerg Roedel To: Shaohua Li Cc: linux-kernel@vger.kernel.org, gang.wei@intel.com, hpa@linux.intel.com, mingo@kernel.org, kernel-team@fb.com, ning.sun@intel.com, srihan@fb.com, alex.eydelberg@intel.com Subject: Re: [RFC] x86/tboot: add an option to disable iommu force on Message-ID: <20170322104900.GE8329@suse.de> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 653 Lines: 17 Hi Shaohua, On Tue, Mar 21, 2017 at 11:37:51AM -0700, Shaohua Li wrote: > IOMMU harms performance signficantly when we run very fast networking > workloads. This is a limitation in hardware based on our observation, so > we'd like to disable the IOMMU force on, but we do want to use TBOOT and > we can sacrifice the DMA security bought by IOMMU. I must admit I know > nothing about TBOOT, but TBOOT guys (cc-ed) think not eabling IOMMU is > totally ok. Can you elaborate a bit more on the setup where the IOMMU still harms network performance? With the recent scalability improvements I measured only a minimal impact on 10GBit networking. Joerg