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 0F1D1C0015E for ; Thu, 3 Aug 2023 07:39:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232940AbjHCHjM (ORCPT ); Thu, 3 Aug 2023 03:39:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231903AbjHCHhb (ORCPT ); Thu, 3 Aug 2023 03:37:31 -0400 Received: from mgamail.intel.com (unknown [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33AE13C21; Thu, 3 Aug 2023 00:36:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1691048190; x=1722584190; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=L0xn3LN+iLDuwnDfC10OXNIFwR0hNYvlK8cIufvM8+I=; b=bMIpammyIwA2nQIhyueXNYbMwDutK/idp4VrBc7VS8I1plJlCLF2jezJ aJ/ydf4tXqe9riQGjcKCFb3vSgL8vQ7f51YKGuh7rms5xz+SuEs/q672D Rya2CxtnqZKC3SpHvxp5BhyYLbSNOh74bAcxmaQQe4k9ozfootN3O/kKD Y8vl03tTkQjO2OYIokZAmfDC4fkix8R4ocTgD50Ur89OPYbPEm6PQdPP1 XUUkgtLA5i678axVPeUezgoBENKxuIp/Sdkrt7siTYqSJ/jphu43I0IiR ED6uG9qq4tOXjfzD9EEKiAaQnqXdEt8DWtDSEroRfeLVNqsyNkym5Pyv2 w==; X-IronPort-AV: E=McAfee;i="6600,9927,10790"; a="368696070" X-IronPort-AV: E=Sophos;i="6.01,251,1684825200"; d="scan'208";a="368696070" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Aug 2023 00:36:22 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10790"; a="764494874" X-IronPort-AV: E=Sophos;i="6.01,251,1684825200"; d="scan'208";a="764494874" Received: from zhaoyuan-mobl.ccr.corp.intel.com (HELO [10.254.213.243]) ([10.254.213.243]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Aug 2023 00:36:16 -0700 Message-ID: <898e9680-3e5c-29d5-39d0-f9648165a2d6@linux.intel.com> Date: Thu, 3 Aug 2023 15:36:13 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Cc: baolu.lu@linux.intel.com, "cohuck@redhat.com" , "eric.auger@redhat.com" , "nicolinc@nvidia.com" , "kvm@vger.kernel.org" , "mjrosato@linux.ibm.com" , "chao.p.peng@linux.intel.com" , "yi.y.sun@linux.intel.com" , "peterx@redhat.com" , "jasowang@redhat.com" , "shameerali.kolothum.thodi@huawei.com" , "lulu@redhat.com" , "suravee.suthikulpanit@amd.com" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "Duan, Zhenzhong" Subject: Re: [PATCH v4 09/12] iommu/vt-d: Add iotlb flush for nested domain To: "Tian, Kevin" , "Liu, Yi L" , "joro@8bytes.org" , "alex.williamson@redhat.com" , "jgg@nvidia.com" , "robin.murphy@arm.com" References: <20230724111335.107427-1-yi.l.liu@intel.com> <20230724111335.107427-10-yi.l.liu@intel.com> <58ae9095-28f2-a44a-b0e5-be82e1eae9d9@linux.intel.com> <40d9b0fa-4a36-c3b7-53bb-4333ff89dc45@linux.intel.com> Content-Language: en-US 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-kselftest@vger.kernel.org On 2023/8/3 12:13, Tian, Kevin wrote: >> From: Baolu Lu >> Sent: Thursday, August 3, 2023 12:06 PM >> >> On 2023/8/3 12:00, Tian, Kevin wrote: >>>> From: Baolu Lu >>>> Sent: Thursday, August 3, 2023 11:25 AM >>>> >>>> On 2023/8/2 15:46, Tian, Kevin wrote: >>>>>> From: Liu, Yi L >>>>>> Sent: Monday, July 24, 2023 7:14 PM >>>>>> >>>>>> + >>>>>> + spin_lock_irqsave(&dmar_domain->lock, flags); >>>>>> + list_for_each_entry(info, &dmar_domain->devices, link) >>>>>> + intel_nested_invalidate(info->dev, dmar_domain, >>>>>> + req->addr, req->npages); >>>>>> + spin_unlock_irqrestore(&dmar_domain->lock, flags); >>>>> >>>>> Disabling interrupt while invalidating iotlb is certainly unacceptable. >>>>> >>>>> Actually there is no need to walk devices. Under dmar_domain there >>>>> is already a list of attached iommu's. >>>> >>>> Walking device is only necessary when invalidating device TLB. For iotlb >>>> invalidation, it only needs to know the iommu's. >>>> >>> >>> even for device tlb we may think whether there is any better way >>> to avoid disabling interrupt. It's a slow path, especially in a guest. >> >> I ever tried this. But some device drivers call iommu_unmap() in the >> interrupt critical path. :-( So we have a long way to go. >> > > emmm... this path only comes from iommufd and the domain is > user-managed. There won't be kernel drivers to call iommu_unmap() > on such domain. Probably we can use a different lock for nested domain and add a comment around the lock with above explanation. Best regards, baolu