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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no 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 4A7D6C83004 for ; Tue, 28 Apr 2020 20:42:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 306A0208FE for ; Tue, 28 Apr 2020 20:42:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726595AbgD1UmD (ORCPT ); Tue, 28 Apr 2020 16:42:03 -0400 Received: from mga12.intel.com ([192.55.52.136]:56480 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726180AbgD1UmC (ORCPT ); Tue, 28 Apr 2020 16:42:02 -0400 IronPort-SDR: hS4L0avMnzi/CbwJb8gTD4tJER3pe08Dhr0lXaZ4WaeQfg/4Q8F+8ekoDI6EtMnf/LCIo+hQsY psN73Cm86GrQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2020 13:42:01 -0700 IronPort-SDR: xagcZJWK38zXxA6Ieuy00Ct62Fx2wWHz9vTb6SOF2J+n3Zp70Y7WRrXkYEqW+/S3sb23RIPidX V9CDHy8qkx/g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,328,1583222400"; d="scan'208";a="246625188" Received: from jpan9-mobl2.amr.corp.intel.com (HELO localhost) ([10.212.240.17]) by orsmga007.jf.intel.com with SMTP; 28 Apr 2020 13:42:00 -0700 Date: Tue, 28 Apr 2020 13:42:00 -0700 From: "Jacob Pan (Jun)" To: "Luck, Tony" Cc: Thomas Gleixner , "Yu, Fenghua" , Ingo Molnar , Borislav Petkov , H Peter Anvin , David Woodhouse , Lu Baolu , "Hansen, Dave" , "Raj, Ashok" , "Jiang, Dave" , "Mehta, Sohil" , "Shankar, Ravi V" , linux-kernel , x86 , "iommu@lists.linux-foundation.org" , jacob.jun.pan@intel.com Subject: Re: [PATCH 5/7] x86/mmu: Allocate/free PASID Message-ID: <20200428134200.000010f7@intel.com> In-Reply-To: <3908561D78D1C84285E8C5FCA982C28F7F608BE9@ORSMSX115.amr.corp.intel.com> References: <1585596788-193989-1-git-send-email-fenghua.yu@intel.com> <1585596788-193989-6-git-send-email-fenghua.yu@intel.com> <87pnbus3du.fsf@nanos.tec.linutronix.de> <20200428112113.000033bd@intel.com> <87tv13o306.fsf@nanos.tec.linutronix.de> <3908561D78D1C84285E8C5FCA982C28F7F608BE9@ORSMSX115.amr.corp.intel.com> Organization: intel X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; i686-w64-mingw32) 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 Tue, 28 Apr 2020 12:07:25 -0700 "Luck, Tony" wrote: > > If fd release cleans up then how should there be something in > > flight at the final mmdrop? > > ENQCMD from the user is only synchronous in that it lets the user > know their request has been added to a queue (or not). Execution of > the request may happen later (if the device is busy working on > requests for other users). The request will take some time to > complete. Someone told me the theoretical worst case once, which I've > since forgotten, but it can be a long time. > > So the driver needs to use flush/drain operations to make sure all > the in-flight work has completed before releasing/re-using the PASID. > Are you suggesting we should let driver also hold a reference of the PASID? > -Tony