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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0126AC433F5 for ; Mon, 25 Apr 2022 15:53:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243060AbiDYP45 (ORCPT ); Mon, 25 Apr 2022 11:56:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243054AbiDYP44 (ORCPT ); Mon, 25 Apr 2022 11:56:56 -0400 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D78045ACE for ; Mon, 25 Apr 2022 08:53:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650902032; x=1682438032; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=OgI7VQnUPjqMWNGxE5sNT1Rye9YtELUHcykl0maLGbY=; b=Bh30bf/fA29fkTaIvRzGNYDS93Qo9O+z3OiwjJ6OP53sNdRd6tvtHEwS Y+nJ/GT4DhE6dFBEgjq+Tgvv4chDC8jkfZSvvrHeV+jJi9wTuIL4bRx8a +V8A7hWt2BoiXbV871HeIJMBqKPM4eLcjOMeaGu1LE0V0LqLfjopwT8D+ I1sHDChx9JKYakzrk3Au1QtzddQLFWotwj4jvzar00IWgeOuf6G1LUxqA fLzXlTsnm/bWLsXN6pJTkvYuYiel+Kgbua45cn5rTLOYc8E1EwFAmTsuS vljzLDZBk2h97DBX/Cmx6876IyBkMyd1QLPrC6PJ+/DHXHFzhBMihciPM w==; X-IronPort-AV: E=McAfee;i="6400,9594,10328"; a="262883593" X-IronPort-AV: E=Sophos;i="5.90,288,1643702400"; d="scan'208";a="262883593" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2022 08:53:51 -0700 X-IronPort-AV: E=Sophos;i="5.90,288,1643702400"; d="scan'208";a="595294518" Received: from bjkrist-mobl.amr.corp.intel.com (HELO [10.212.88.70]) ([10.212.88.70]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2022 08:53:50 -0700 Message-ID: <22b659c7-e972-7a56-2bd7-8df3b4820d4e@intel.com> Date: Mon, 25 Apr 2022 08:55:46 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit Content-Language: en-US To: Jean-Philippe Brucker Cc: "zhangfei.gao@foxmail.com" , Fenghua Yu , Joerg Roedel , Ravi V Shankar , Tony Luck , Ashok Raj , Peter Zijlstra , Dave Hansen , x86 , linux-kernel , iommu , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Josh Poimboeuf , Thomas Gleixner , will@kernel.org, robin.murphy@arm.com, zhangfei.gao@linaro.org References: <76ec6342-0d7c-7c7b-c132-2892e4048fa1@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/25/22 07:26, Jean-Philippe Brucker wrote: >> >> How does the IOMMU hardware know that all activity to a given PASID is >> finished? That activity should, today, be independent of an mm or a >> fd's lifetime. > In the case of uacce, it's tied to the fd lifetime: opening an accelerator > queue calls iommu_sva_bind_device(), which sets up the PASID context in > the IOMMU. Closing the queue calls iommu_sva_unbind_device() which > destroys the PASID context (after the device driver stopped all DMA for > this PASID). Could this PASID context destruction move from being "fd-based" to happening under mm_pasid_drop()? Logically, it seems like that should work because mm_pasid_drop() happens after exit_mmap() where the VMAs (which hold references to 'struct file' via vma->vm_file) are torn down.