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 0CC88C10F03 for ; Thu, 25 Apr 2019 07:40:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8943217FA for ; Thu, 25 Apr 2019 07:40:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727521AbfDYHkh (ORCPT ); Thu, 25 Apr 2019 03:40:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44202 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727004AbfDYHkh (ORCPT ); Thu, 25 Apr 2019 03:40:37 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E2D2130882A5; Thu, 25 Apr 2019 07:40:36 +0000 (UTC) Received: from [10.36.116.17] (ovpn-116-17.ams2.redhat.com [10.36.116.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9FDF01001DDE; Thu, 25 Apr 2019 07:40:33 +0000 (UTC) Subject: Re: [PATCH v2 09/19] iommu/vt-d: Enlightened PASID allocation To: "Liu, Yi L" , Jacob Pan , "iommu@lists.linux-foundation.org" , LKML , Joerg Roedel , David Woodhouse , Alex Williamson , Jean-Philippe Brucker Cc: "Tian, Kevin" , "Raj, Ashok" , Christoph Hellwig , Lu Baolu , Andriy Shevchenko 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> From: Auger Eric Message-ID: Date: Thu, 25 Apr 2019 09:40:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Thu, 25 Apr 2019 07:40:37 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ;-) Thanks Eric > > Thanks, > Yi Liu >