linux-kernel - Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc

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Message-ID: <05dec0b1-61ac-c3af-e238-322c1eec57ec@intel.com>
Date:   Sat, 7 Oct 2023 17:38:17 +0800
From:   Yi Liu <yi.l.liu@...el.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>
CC:     Robin Murphy <robin.murphy@....com>,
        Baolu Lu <baolu.lu@...ux.intel.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Duan, Zhenzhong" <zhenzhong.duan@...el.com>,
        "Martins, Joao" <joao.m.martins@...cle.com>
Subject: Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for
 domain_alloc_user op

On 2023/9/27 09:08, Tian, Kevin wrote:
>> From: Jason Gunthorpe <jgg@...dia.com>
>> Sent: Wednesday, September 27, 2023 12:29 AM
>>
>> On Tue, Sep 26, 2023 at 06:37:55AM +0000, Tian, Kevin wrote:
>>>> From: Robin Murphy <robin.murphy@....com>
>>>> Sent: Friday, September 22, 2023 5:48 PM
>>>>
>>>> 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).
>>>>
>>>
>>> IOMMU_HWPT_TYPE_KERNEL then?
>>>
>>> IOMMU_HWPT_TYPE_GENERIC also doesn't sound a straight word.
>>
>> At the end of the day this enum is the type tag for:
>>
>>   struct iommu_hwpt_alloc {
>>   	__u32 size;
>>   	__u32 pt_id;
>>   	__u32 out_hwpt_id;
>>   	__u32 __reserved;
>> +	__u32 hwpt_type;
>> +	__u32 data_len;
>> +	__aligned_u64 data_uptr;
>>   };
>>
>> That pointer.
>>
>> IOMMU_HWPT_ALLOC_DATA_NONE = 0
>> IOMMU_HWPT_ALLOC_DATA_INTEL_VTD
>> IOMMU_HWPT_ALLOC_DATA_ARM_SMMUV3
>>
>> etc?
>>
>> DATA_NONE requires data_len == 0
>>
> 
> Looks good. Probably hwpt_type can be also renamed to data_type
> to better match this interpretation.

ack.

-- 
Regards,
Yi Liu