Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc_user op

[Nicolin Chen <nicolinc@nvidia.com>]

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:

/**
 * 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:

// 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