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

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Date:   Mon, 16 Oct 2023 11:28:15 +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 2023/10/14 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.

> 
> /**
>   * enum iommu_hwpt_data_type - IOMMU HWPT Data Type
>   * @IOMMU_HWPT_DATA_NONE: no data
>   * @IOMMU_HWPT_DATA_VTD_S1: Intel VT-d stage-1 page table
>   * @IOMMU_HWPT_DATA_ARM_SMMUV3: ARM SMMUv3 Context Descriptor Table
>   */
> enum iommu_hwpt_data_type {
> 	IOMMU_HWPT_DATA_NONE,
> 	IOMMU_HWPT_DATA_VTD_S1,
> 	IOMMU_HWPT_DATA_ARM_SMMUV3,
> };
> 
> Though inevitably we'd have to define a separate data group for
> things like set_dev_data that is related to idev v.s. hwpt:

yes, the type field is in separate data group per path.

> 
> // IOMMU_DEV_DATA_TYPE sounds like an IOMMU device, other than a
> // passthrough device, so renaming to "_IDEV_" here. And perhaps
> // "set_dev_data" could be "set_idev_data" too? Any better name?
> 
> /**
>   * enum iommu_idev_data_type - Data Type for a Device behind an IOMMU
>   * @IOMMU_IDEV_DATA_NONE: no data
>   * @IOMMU_IDEV_DATA_ARM_SMMUV3: ARM SMMUv3 specific device data
>   */
> enum iommu_idev_data_type {
> 	IOMMU_IDEV_DATA_NONE,
> 	IOMMU_IDEV_DATA_ARM_SMMUV3,
> };
> 
> /**
>   * struct iommu_idev_data_arm_smmuv3 - ARM SMMUv3 specific device data
>   * @sid: The Stream ID that is assigned in the user space
>   *
>   * The SMMUv3 specific user space data for a device that is behind an SMMU HW.
>   * The guest-level user data should be linked to the host-level kernel data,
>   * which will be used by user space cache invalidation commands.
>   */
> struct iommu_idev_data_arm_smmuv3 {
> 	__u32 sid;
> };
> 
> /**
>   * struct iommu_set_idev_data - ioctl(IOMMU_SET_IDEV_DATA)
>   * @size: sizeof(struct iommu_set_idev_data)
>   * @dev_id: The device to set an iommu specific device data
>   * @data_uptr: User pointer of the device user data
>   * @data_len: Length of the device user data
>   *
>   * The device data must be unset using ioctl(IOMMU_UNSET_IDEV_DATA), before
>   * another ioctl(IOMMU_SET_IDEV_DATA) call or before the device itself gets
>   * unbind'd from the iommufd context.
>   */
> struct iommu_set_idev_data {
> 	__u32 size;
> 	__u32 dev_id;
> 	__aligned_u64 data_uptr;
> 	__u32 data_len;
> };
> 
> Thanks
> Nic

-- 
Regards,
Yi Liu