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 A4B65CD4F45 for ; Fri, 22 Sep 2023 09:48:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229572AbjIVJsK (ORCPT ); Fri, 22 Sep 2023 05:48:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229497AbjIVJsK (ORCPT ); Fri, 22 Sep 2023 05:48:10 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id EB7F78F; Fri, 22 Sep 2023 02:48:03 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AD60DDA7; Fri, 22 Sep 2023 02:48:40 -0700 (PDT) Received: from [10.57.0.85] (unknown [10.57.0.85]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 905653F67D; Fri, 22 Sep 2023 02:47:57 -0700 (PDT) Message-ID: Date: Fri, 22 Sep 2023 10:47:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc_user op Content-Language: en-GB To: Jason Gunthorpe , Baolu Lu Cc: Yi Liu , joro@8bytes.org, alex.williamson@redhat.com, kevin.tian@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, zhenzhong.duan@intel.com, joao.m.martins@oracle.com References: <20230921075138.124099-1-yi.l.liu@intel.com> <20230921075138.124099-2-yi.l.liu@intel.com> <0d37a1b1-e7ef-fa73-d17c-629cd254ae75@linux.intel.com> <20230921164447.GQ13733@nvidia.com> From: Robin Murphy In-Reply-To: <20230921164447.GQ13733@nvidia.com> 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 2023-09-21 17:44, Jason Gunthorpe wrote: > On Thu, Sep 21, 2023 at 08:12:03PM +0800, Baolu Lu wrote: >> On 2023/9/21 15:51, Yi Liu wrote: >>> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h >>> index 4a7c5c8fdbb4..3c8660fe9bb1 100644 >>> --- a/include/uapi/linux/iommufd.h >>> +++ b/include/uapi/linux/iommufd.h >>> @@ -357,6 +357,14 @@ enum iommufd_hwpt_alloc_flags { >>> IOMMU_HWPT_ALLOC_NEST_PARENT = 1 << 0, >>> }; >>> +/** >>> + * enum iommu_hwpt_type - IOMMU HWPT Type >>> + * @IOMMU_HWPT_TYPE_DEFAULT: default >> >> How about s/default/vendor agnostic/ ? > > Please don't use the word vendor :) > > IOMMU_HWPT_TYPE_GENERIC perhaps if we don't like default Ah yes, a default domain type, not to be confused with any default domain type, including the default default domain type. Just in case anyone had forgotten how gleefully fun this is :D I particularly like the bit where we end up with this construct later: switch (hwpt_type) { case IOMMU_HWPT_TYPE_DEFAULT: /* allocate a domain */ default: /* allocate a different domain */ } But of course neither case allocates a *default* domain, because it's quite obviously the wrong place to be doing that. I could go on enjoying myself, but basically yeah, "default" can't be a type in itself (at best it would be a meta-type which could be requested, such that it resolves to some real type to actually allocate), so a good name should reflect what the type functionally *means* to the user. IIUC the important distinction is that it's an abstract kernel-owned pagetable for the user to indirectly control via the API, rather than one it owns and writes directly (and thus has to be in a specific agreed format). Thanks, Robin.