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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 00D28C2BB55 for ; Thu, 16 Apr 2020 15:13:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1CC6214AF for ; Thu, 16 Apr 2020 15:13:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hfkI7db0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731798AbgDPPN0 (ORCPT ); Thu, 16 Apr 2020 11:13:26 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:36276 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2395091AbgDPPMj (ORCPT ); Thu, 16 Apr 2020 11:12:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587049958; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rBW9oZnC7o7UHDZIGFKToXwrEuLBhCPll+eChHTjsyQ=; b=hfkI7db0UKmGb7GAyFaqVOPItAQhq7eGScZPeKeoNGkGjBQ7A8Ftar2RNrcXuGPtb1UFAs mTATgzpvg8YhCkpuFeFrzii/fH6+qAmM61bWM3QfkoaxAh6gDOGjaYiV+0unyqYbUY2O5L VNlKYXU9ACvXeuo2nd2AqOCroPeGSY8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-66-4JsCiRBvPDaurYyCFFs7lA-1; Thu, 16 Apr 2020 11:12:34 -0400 X-MC-Unique: 4JsCiRBvPDaurYyCFFs7lA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3A89D800D5C; Thu, 16 Apr 2020 15:12:32 +0000 (UTC) Received: from [10.36.115.53] (ovpn-115-53.ams2.redhat.com [10.36.115.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6C4AB7E7D1; Thu, 16 Apr 2020 15:12:22 +0000 (UTC) Subject: Re: [PATCH v1 7/8] vfio/type1: Add VFIO_IOMMU_CACHE_INVALIDATE To: "Tian, Kevin" , "Liu, Yi L" , Alex Williamson Cc: "jacob.jun.pan@linux.intel.com" , "joro@8bytes.org" , "Raj, Ashok" , "Tian, Jun J" , "Sun, Yi Y" , "jean-philippe@linaro.org" , "peterx@redhat.com" , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Wu, Hao" References: <1584880325-10561-1-git-send-email-yi.l.liu@intel.com> <1584880325-10561-8-git-send-email-yi.l.liu@intel.com> <20200402142428.2901432e@w520.home> <20200403093436.094b1928@w520.home> <7d13bdbb-e972-c301-0970-90f63ecf69fc@redhat.com> From: Auger Eric Message-ID: <4f7de577-dee7-91db-bc8c-637558016673@redhat.com> Date: Thu, 16 Apr 2020 17:12:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Kevin, On 4/16/20 3:28 PM, Tian, Kevin wrote: >> From: Auger Eric >> Sent: Thursday, April 16, 2020 8:43 PM >> >> Hi Kevin, >> On 4/16/20 2:09 PM, Tian, Kevin wrote: >>>> From: Liu, Yi L >>>> Sent: Thursday, April 16, 2020 6:40 PM >>>> >>>> Hi Alex, >>>> Still have a direction question with you. Better get agreement with you >>>> before heading forward. >>>> >>>>> From: Alex Williamson >>>>> Sent: Friday, April 3, 2020 11:35 PM >>>> [...] >>>>>>>> + * >>>>>>>> + * returns: 0 on success, -errno on failure. >>>>>>>> + */ >>>>>>>> +struct vfio_iommu_type1_cache_invalidate { >>>>>>>> + __u32 argsz; >>>>>>>> + __u32 flags; >>>>>>>> + struct iommu_cache_invalidate_info cache_info; >>>>>>>> +}; >>>>>>>> +#define VFIO_IOMMU_CACHE_INVALIDATE _IO(VFIO_TYPE, >>>>> VFIO_BASE >>>>>>> + 24) >>>>>>> >>>>>>> The future extension capabilities of this ioctl worry me, I wonder if >>>>>>> we should do another data[] with flag defining that data as >>>> CACHE_INFO. >>>>>> >>>>>> Can you elaborate? Does it mean with this way we don't rely on iommu >>>>>> driver to provide version_to_size conversion and instead we just pass >>>>>> data[] to iommu driver for further audit? >>>>> >>>>> No, my concern is that this ioctl has a single function, strictly tied >>>>> to the iommu uapi. If we replace cache_info with data[] then we can >>>>> define a flag to specify that data[] is struct >>>>> iommu_cache_invalidate_info, and if we need to, a different flag to >>>>> identify data[] as something else. For example if we get stuck >>>>> expanding cache_info to meet new demands and develop a new uapi to >>>>> solve that, how would we expand this ioctl to support it rather than >>>>> also create a new ioctl? There's also a trade-off in making the ioctl >>>>> usage more difficult for the user. I'd still expect the vfio layer to >>>>> check the flag and interpret data[] as indicated by the flag rather >>>>> than just passing a blob of opaque data to the iommu layer though. >>>>> Thanks, >>>> >>>> Based on your comments about defining a single ioctl and a unified >>>> vfio structure (with a @data[] field) for pasid_alloc/free, bind/ >>>> unbind_gpasid, cache_inv. After some offline trying, I think it would >>>> be good for bind/unbind_gpasid and cache_inv as both of them use the >>>> iommu uapi definition. While the pasid alloc/free operation doesn't. >>>> It would be weird to put all of them together. So pasid alloc/free >>>> may have a separate ioctl. It would look as below. Does this direction >>>> look good per your opinion? >>>> >>>> ioctl #22: VFIO_IOMMU_PASID_REQUEST >>>> /** >>>> * @pasid: used to return the pasid alloc result when flags == >> ALLOC_PASID >>>> * specify a pasid to be freed when flags == FREE_PASID >>>> * @range: specify the allocation range when flags == ALLOC_PASID >>>> */ >>>> struct vfio_iommu_pasid_request { >>>> __u32 argsz; >>>> #define VFIO_IOMMU_ALLOC_PASID (1 << 0) >>>> #define VFIO_IOMMU_FREE_PASID (1 << 1) >>>> __u32 flags; >>>> __u32 pasid; >>>> struct { >>>> __u32 min; >>>> __u32 max; >>>> } range; >>>> }; >>>> >>>> ioctl #23: VFIO_IOMMU_NESTING_OP >>>> struct vfio_iommu_type1_nesting_op { >>>> __u32 argsz; >>>> __u32 flags; >>>> __u32 op; >>>> __u8 data[]; >>>> }; >>>> >>>> /* Nesting Ops */ >>>> #define VFIO_IOMMU_NESTING_OP_BIND_PGTBL 0 >>>> #define VFIO_IOMMU_NESTING_OP_UNBIND_PGTBL 1 >>>> #define VFIO_IOMMU_NESTING_OP_CACHE_INVLD 2 >>>> >>> >>> Then why cannot we just put PASID into the header since the >>> majority of nested usage is associated with a pasid? >>> >>> ioctl #23: VFIO_IOMMU_NESTING_OP >>> struct vfio_iommu_type1_nesting_op { >>> __u32 argsz; >>> __u32 flags; >>> __u32 op; >>> __u32 pasid; >>> __u8 data[]; >>> }; >>> >>> In case of SMMUv2 which supports nested w/o PASID, this field can >>> be ignored for that specific case. >> On my side I would prefer keeping the pasid in the data[]. This is not >> always used. >> >> For instance, in iommu_cache_invalidate_info/iommu_inv_pasid_info we >> devised flags to tell whether the PASID is used. >> > > But don't we include a PASID in both invalidate structures already? The pasid presence is indicated by the IOMMU_INV_ADDR_FLAGS_PASID flag. For instance for nested stage SMMUv3 I current performs an ARCHID (asid) based invalidation only. Eric > > struct iommu_inv_addr_info { > #define IOMMU_INV_ADDR_FLAGS_PASID (1 << 0) > #define IOMMU_INV_ADDR_FLAGS_ARCHID (1 << 1) > #define IOMMU_INV_ADDR_FLAGS_LEAF (1 << 2) > __u32 flags; > __u32 archid; > __u64 pasid; > __u64 addr; > __u64 granule_size; > __u64 nb_granules; > }; > > struct iommu_inv_pasid_info { > #define IOMMU_INV_PASID_FLAGS_PASID (1 << 0) > #define IOMMU_INV_PASID_FLAGS_ARCHID (1 << 1) > __u32 flags; > __u32 archid; > __u64 pasid; > }; > > then consolidating the pasid field into generic header doesn't > hurt. the specific handler still rely on flags to tell whether it > is used? > > Thanks > Kevin >