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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 1C8E8C43219 for ; Thu, 25 Apr 2019 23:00:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40D7E206BF for ; Thu, 25 Apr 2019 23:00:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729242AbfDYW7O (ORCPT ); Thu, 25 Apr 2019 18:59:14 -0400 Received: from mga02.intel.com ([134.134.136.20]:9849 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727208AbfDYW7O (ORCPT ); Thu, 25 Apr 2019 18:59:14 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Apr 2019 15:59:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,395,1549958400"; d="scan'208";a="294613245" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga004.jf.intel.com with ESMTP; 25 Apr 2019 15:59:13 -0700 Date: Thu, 25 Apr 2019 16:01:56 -0700 From: Jacob Pan To: Auger Eric Cc: "Liu, Yi L" , "iommu@lists.linux-foundation.org" , LKML , Joerg Roedel , David Woodhouse , Alex Williamson , Jean-Philippe Brucker , "Tian, Kevin" , "Raj, Ashok" , Christoph Hellwig , Lu Baolu , Andriy Shevchenko , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v2 09/19] iommu/vt-d: Enlightened PASID allocation Message-ID: <20190425160156.4f5decaa@jacob-builder> In-Reply-To: References: <1556062279-64135-1-git-send-email-jacob.jun.pan@linux.intel.com> <1556062279-64135-10-git-send-email-jacob.jun.pan@linux.intel.com> <143adac1-d58b-dde6-593b-74ea71da73c8@redhat.com> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Apr 2019 09:40:31 +0200 Auger Eric wrote: > Hi Liu, > > On 4/25/19 9:12 AM, Liu, Yi L wrote: > > Hi Eric, > > > >> From: Auger Eric [mailto:eric.auger@redhat.com] > >> Sent: Thursday, April 25, 2019 1:28 AM > >> To: Jacob Pan ; > >> iommu@lists.linux-foundation.org; Subject: Re: [PATCH v2 09/19] > >> iommu/vt-d: Enlightened PASID allocation > >> > >> Hi Jacob, > >> > >> On 4/24/19 1:31 AM, Jacob Pan wrote: > >>> From: Lu Baolu > >>> > >>> If Intel IOMMU runs in caching mode, a.k.a. virtual IOMMU, the > >>> IOMMU driver should rely on the emulation software to allocate > >>> and free PASID IDs. > >> Do we make the decision depending on the CM or depending on the > >> VCCAP_REG? > >> > >> VCCAP_REG description says: > >> > >> If Set, software must use Virtual Command Register interface to > >> allocate and free PASIDs. > > > > The answer is it depends on the ECAP.VCS and then the PASID > > allocation bit in VCCAP_REG. But VCS bit implies the iommu is a > > software implementation (vIOMMU) of vt-d architecture. Pls refer to > > the descriptions of "Virtual Command Support" in vt-d 3.0 spec. > > > > "Hardware implementations of this architecture report a value of 0 > > in this field. Software implementations (emulation) of this > > architecture may report VCS=1." > > OK I understand. But strictly speaking a vIOMMU may not implement CM. > But that's nitpicking ;-) > CAP.CM (caching mode) and ECAP.VCS(virtual command support) are separate. I think we are mixing the two here since both are sufficient condition to indicate whether we are running in a guest. > Thanks > > Eric > > > > Thanks, > > Yi Liu > > [Jacob Pan]