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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B2EF3C83000 for ; Tue, 28 Apr 2020 19:07:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9797B20730 for ; Tue, 28 Apr 2020 19:07:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728797AbgD1TH1 convert rfc822-to-8bit (ORCPT ); Tue, 28 Apr 2020 15:07:27 -0400 Received: from mga04.intel.com ([192.55.52.120]:45384 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728547AbgD1TH1 (ORCPT ); Tue, 28 Apr 2020 15:07:27 -0400 IronPort-SDR: ZNywR7xBh6y98kbCcwl7O6hkSRmqErZMF3dnMLQpnbn9cvcs5+7Ermir0Fylp52DTgRxOMOeO0 jkbXM8k+iZGg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2020 12:07:26 -0700 IronPort-SDR: H9WMt1ccVsFYYldEOJJiXYnUjdrg0S5E87Hcxdt2iFCHphHKG0StdfXzj9GjiUZAd+NHrqTEpG AJy/ZUPIkUAA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,328,1583222400"; d="scan'208";a="459331916" Received: from orsmsx103.amr.corp.intel.com ([10.22.225.130]) by fmsmga006.fm.intel.com with ESMTP; 28 Apr 2020 12:07:26 -0700 Received: from orsmsx160.amr.corp.intel.com (10.22.226.43) by ORSMSX103.amr.corp.intel.com (10.22.225.130) with Microsoft SMTP Server (TLS) id 14.3.439.0; Tue, 28 Apr 2020 12:07:26 -0700 Received: from orsmsx115.amr.corp.intel.com ([169.254.4.83]) by ORSMSX160.amr.corp.intel.com ([169.254.13.187]) with mapi id 14.03.0439.000; Tue, 28 Apr 2020 12:07:26 -0700 From: "Luck, Tony" To: Thomas Gleixner , "Pan, Jacob jun" CC: "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" , "Pan, Jacob jun" Subject: RE: [PATCH 5/7] x86/mmu: Allocate/free PASID Thread-Topic: [PATCH 5/7] x86/mmu: Allocate/free PASID Thread-Index: AQHWBtMgRqn1rM/ldEi9589O6eqhDKiMHSGAgANeKoCAAAkqgP//jPrQ Date: Tue, 28 Apr 2020 19:07:25 +0000 Message-ID: <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> In-Reply-To: <87tv13o306.fsf@nanos.tec.linutronix.de> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-version: 11.2.0.6 dlp-reaction: no-action x-originating-ip: [10.22.254.140] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 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. -Tony