linux-kernel - Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT

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Message-ID: <8c05763d-1668-4b99-af35-b43a34e966c2@intel.com>
Date:   Mon, 11 Dec 2023 15:53:40 +0800
From:   Yi Liu <yi.l.liu@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        "Tian, Kevin" <kevin.tian@...el.com>
CC:     "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.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>,
        "joao.m.martins@...cle.com" <joao.m.martins@...cle.com>,
        "Zeng, Xin" <xin.zeng@...el.com>,
        "Zhao, Yan Y" <yan.y.zhao@...el.com>
Subject: Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE

On 2023/12/7 22:42, Jason Gunthorpe wrote:
> On Thu, Dec 07, 2023 at 09:04:00AM +0000, Tian, Kevin wrote:
>>> From: Liu, Yi L <yi.l.liu@...el.com>
>>> Sent: Thursday, December 7, 2023 2:59 PM
>>>
>>> On 2023/11/17 21:07, Yi Liu wrote:
>>>> @@ -613,4 +614,38 @@ struct iommu_hwpt_get_dirty_bitmap {
>>>>    #define IOMMU_HWPT_GET_DIRTY_BITMAP _IO(IOMMUFD_TYPE, \
>>>>
>>> 	IOMMUFD_CMD_HWPT_GET_DIRTY_BITMAP)
>>>>
>>>> +/**
>>>> + * struct iommu_hwpt_invalidate - ioctl(IOMMU_HWPT_INVALIDATE)
>>>> + * @size: sizeof(struct iommu_hwpt_invalidate)
>>>> + * @hwpt_id: HWPT ID of a nested HWPT for cache invalidation
>>>> + * @reqs_uptr: User pointer to an array having @req_num of cache
>>> invalidation
>>>> + *             requests. The request entries in the array are of fixed width
>>>> + *             @req_len, and contain a user data structure for invalidation
>>>> + *             request specific to the given hardware page table.
>>>> + * @req_type: One of enum iommu_hwpt_data_type, defining the data
>>> type of all
>>>> + *            the entries in the invalidation request array. It should suit
>>>> + *            with the data_type passed per the allocation of the hwpt pointed
>>>> + *            by @hwpt_id.
>>>
>>> @Jason and Kevin,
>>>
>>> Here a check with you two. I had a conversation with Nic on the definition
>>> of req_type here. It was added to support potential multiple kinds of cache
>>> invalidation data types for a invalidating cache for a single hwpt type[1].
>>> But we defined it as reusing the hwpt_data_type. In this way, it is not
>>> able to support the potential case in[1]. is it? Shall we define a separate
>>> enum for invalidation data types? And how can we let user know the
>>> available invalidation data types for a hwpt type? Any idea?
>>>
>>> [1] https://lore.kernel.org/linux-
>>> iommu/20231018163720.GA3952@...dia.com/
>>>
>>
>>  From that thread Jason mentioned to make the invalidation format
>> part of domain allocation. If that is the direction to go then there
>> won't be multiple invalidation formats per hwpt. The user should
>> create multiple hwpt's per invalidation format (though mixing
>> formats in one virtual platform is very unlikely)?
> 
> I think we could do either, but I have a vauge cleanness preference
> that the enums are just different? That would follow a pretty typical
> pattern for a structure tag to reflect the content of the structure.

Is this still following the direction to make the invalidation format
part of domain allocation?

-- 
Regards,
Yi Liu