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 2FCAAC43334 for ; Wed, 15 Jun 2022 13:10:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242888AbiFONKd (ORCPT ); Wed, 15 Jun 2022 09:10:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233309AbiFONKc (ORCPT ); Wed, 15 Jun 2022 09:10:32 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95F9F24084 for ; Wed, 15 Jun 2022 06:10:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1655298628; x=1686834628; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=49iVnIBH2iZUFVwoFe1umaO203mLoJXO8qFijdhPPbM=; b=F2iVngdVStwwwRWa87iUVrCMrnbpBCKyjJ1/hxAlxenfW/GEJ93wU/Z2 JzNdiW+60mSwc0YW8cJXUAOLkiMYLtEyNvRlgDrUqshbZqzrRjzz3c71t qU9hC4dMEx42Emd9SPHewL3uHbp7UQ9DHxUI4u0kpDg9Y2DB3Ce4p3YUq YFwQMlOCdbgBcSfuGRBXl39zkA7Bm0yRC1NIHzuN9+PVUJcIAdSKvHeUF NDi8tTzRZHGffVvvQYe8IIVQ5bQXYjvR+a7LMCCbWyTDHhDjCd0mVJi4d Umn8vobZMOwfWZsdFpgy+BTK19UO3wR0l5RKVp+rXcmrofNotyEnU0RJY Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10378"; a="279672546" X-IronPort-AV: E=Sophos;i="5.91,302,1647327600"; d="scan'208";a="279672546" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jun 2022 06:10:25 -0700 X-IronPort-AV: E=Sophos;i="5.91,302,1647327600"; d="scan'208";a="589105904" Received: from leitan-mobl.ccr.corp.intel.com (HELO [10.255.31.142]) ([10.255.31.142]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jun 2022 06:10:21 -0700 Message-ID: Date: Wed, 15 Jun 2022 21:10:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Cc: baolu.lu@linux.intel.com, Will Deacon , Robin Murphy , "Liu, Yi L" , "Pan, Jacob jun" , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2 03/12] iommu/vt-d: Remove clearing translation data in disable_dmar_iommu() Content-Language: en-US To: "Tian, Kevin" , Joerg Roedel , "Raj, Ashok" , Christoph Hellwig , Jason Gunthorpe References: <20220614025137.1632762-1-baolu.lu@linux.intel.com> <20220614025137.1632762-4-baolu.lu@linux.intel.com> <28161d94-6f2d-700f-853d-53b42f4d00d0@linux.intel.com> From: Baolu Lu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/6/15 14:22, Tian, Kevin wrote: >> From: Baolu Lu >> Sent: Tuesday, June 14, 2022 3:21 PM >> >> On 2022/6/14 14:49, Tian, Kevin wrote: >>>> From: Lu Baolu >>>> Sent: Tuesday, June 14, 2022 10:51 AM >>>> >>>> The disable_dmar_iommu() is called when IOMMU initialization fails or >>>> the IOMMU is hot-removed from the system. In both cases, there is no >>>> need to clear the IOMMU translation data structures for devices. >>>> >>>> On the initialization path, the device probing only happens after the >>>> IOMMU is initialized successfully, hence there're no translation data >>>> structures. >>> Out of curiosity. With kexec the IOMMU may contain stale mappings >>> from the old kernel. Then is it meaningful to disable IOMMU after the >>> new kernel fails to initialize it properly? >> >> For kexec kernel, if the IOMMU is detected to be pre-enabled, the IOMMU >> driver will try to copy tables from the old kernel. If copying table >> fails, the IOMMU driver will disable IOMMU and do the normal >> initialization. >> > > What about an error occurred after copying table in the initialization > path? The new kernel will be in a state assuming iommu is disabled > but it is still enabled using an old mapping for certain devices... > If copying table failed, the translation will be disabled and a clean root table will be used. if (translation_pre_enabled(iommu)) { pr_info("Translation already enabled - trying to copy translation structures\n"); ret = copy_translation_tables(iommu); if (ret) { /* * We found the IOMMU with translation * enabled - but failed to copy over the * old root-entry table. Try to proceed * by disabling translation now and * allocating a clean root-entry table. * This might cause DMAR faults, but * probably the dump will still succeed. */ pr_err("Failed to copy translation tables from previous kernel for %s\n", iommu->name); iommu_disable_translation(iommu); clear_translation_pre_enabled(iommu); } else { pr_info("Copied translation tables from previous kernel for %s\n", iommu->name); } } Best regards, baolu