From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754830Ab1KNPMA (ORCPT ); Mon, 14 Nov 2011 10:12:00 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:34479 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751632Ab1KNPL6 (ORCPT ); Mon, 14 Nov 2011 10:11:58 -0500 Message-ID: <4EC210CB.1010409@gmail.com> Date: Mon, 14 Nov 2011 23:12:11 -0800 From: cody User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.16) Gecko/20110818 Icedove/3.0.11 MIME-Version: 1.0 To: David Woodhouse CC: Chris Wright , Roland Dreier , Alex Williamson , iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, ddutile@redhat.com Subject: Re: [PATCH] intel-iommu: Default to non-coherent for domains unattached to iommus References: <20111111224849.9756.13368.stgit@bling.home> <1321058267.2006.21.camel@shinybook.infradead.org> <20111112005100.GR14486@sequoia.sous-sol.org> <1321059340.2006.27.camel@shinybook.infradead.org> <20111112010850.GT14486@sequoia.sous-sol.org> <1321060841.2006.35.camel@shinybook.infradead.org> In-Reply-To: <1321060841.2006.35.camel@shinybook.infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/11/2011 05:20 PM, David Woodhouse wrote: > On Fri, 2011-11-11 at 17:08 -0800, Chris Wright wrote: > >> All the stale PTE issues I've encountered in the past have turned into >> fixed sw bugs (perhaps it's since been fixed?). Also, I thought with >> Coherency On/Off it's only effecting the use of clflush, not IOTLB or >> Context Entry cache flushing (invalidations). >> > Yeah, it's supposed to be *just* clflush. Nevertheless, I can imagine it > being screwed up and there actually being a buffer in the chipset too. > We certainly made that mistake with the graphics engine in some cases... > > >> On a slightly separate, but performance related note...have you ever >> tried using the hw queue? Currently we only have a sw queue, but the >> submission path for invalidations doesn't really queue (unless I missed >> it). It seems to pull from the software queue and submit/wait, >> submit/wait...Seems simple enough to submit the whole queue and then >> issue the wait. >> > I have a feeling we trigger errata if we do that — although if we're > only doing it for an emulated IOMMU that shouldn't be an issue. > > What does the emulated IOMMU here? Does it mean the emulated IOMMU exposed to guest VM?