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

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Message-ID: <2a86074f-94a9-667d-6e94-c582d49b7588@intel.com>
Date:   Tue, 17 Oct 2023 16:51:40 +0800
From:   Yi Liu <yi.l.liu@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>
CC:     <joro@...tes.org>, <alex.williamson@...hat.com>,
        <kevin.tian@...el.com>, <robin.murphy@....com>,
        <baolu.lu@...ux.intel.com>, <cohuck@...hat.com>,
        <eric.auger@...hat.com>, <kvm@...r.kernel.org>,
        <mjrosato@...ux.ibm.com>, <chao.p.peng@...ux.intel.com>,
        <yi.y.sun@...ux.intel.com>, <peterx@...hat.com>,
        <jasowang@...hat.com>, <shameerali.kolothum.thodi@...wei.com>,
        <lulu@...hat.com>, <suravee.suthikulpanit@....com>,
        <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>, <zhenzhong.duan@...el.com>,
        <joao.m.martins@...cle.com>
Subject: Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for
 domain_alloc_user op

On 2023/10/17 02:17, Nicolin Chen wrote:
> On Mon, Oct 16, 2023 at 08:54:07AM -0300, Jason Gunthorpe wrote:
>> On Mon, Oct 16, 2023 at 11:28:15AM +0800, Yi Liu wrote:
>>> On 2023/10/14 01:56, Nicolin Chen wrote:
>>>> On Fri, Oct 13, 2023 at 11:04:56AM -0300, Jason Gunthorpe wrote:
>>>>> On Fri, Oct 13, 2023 at 12:33:13PM +0800, Yi Liu wrote:
>>>>>
>>>>>> not really. Below the users of the struct iommu_user_data in my current
>>>>>> iommufd_nesting branch. Only the domain_alloc_user op has type as there
>>>>>> can be multiple vendor specific alloc data types. Basically, I'm ok to
>>>>>> make the change you suggested, just not sure if it is good to add type
>>>>>> as it is only needed by one path.
>>>>>
>>>>> I don't think we should ever have an opaque data blob without a type
>>>>> tag..
>>>>
>>>> I can add those "missing" data types, and then a driver will be
>>>> responsible for sanitizing the type along with the data_len.
>>>>
>>>> I notice that the enum iommu_hwpt_data_type in the posted patch
>>>> is confined to the alloc_user uAPI. Perhaps we should share it
>>>> with invalidate too:
>>>
>>> invalidation path does not need a type field today as the data
>>> type is vendor specific, vendor driver should know the data type
>>> when calls in.
>>
>> I'm not keen on that, what if a driver needs another type in the
>> future?  You'd want to make the invalidation data format part of the
>> domain allocation?
> 
> The invalidation data has hwpt_id so it's tied to a hwpt and its
> hwpt->domain. Would it be reasonable to have a different type of
> invalidation data for the same type of hwpt?

this seems like what Jason asks. A type of hwpt can have two kinds
of invalidation data types. Is it really possible?

> With this being asked, I added it for our next version. At this
> moment, it only does a sanity job:
> 
> // API
> __iommu_copy_struct_from_user(void *dst_data,
> 			      const struct iommu_user_data *src_data,
> 			      unsigned int data_type, size_t data_len,
> 			      size_t min_len)
> {
> 	if (src_data->type != data_type)
> 		return -EINVAL;
> 
> // Caller
> 	rc = iommu_copy_struct_from_user(&user_cfg, user_data,
> 					 IOMMU_HWPT_DATA_SELFTEST, iotlb);
> 	if (rc)
> 		return ERR_PTR(rc);
> 
> Thanks
> Nic

-- 
Regards,
Yi Liu