RE: [PATCH v3 01/10] iommufd: Add data structure for Intel VT-d stage-1 domain allocation

Tian, Kevin
2023-05-24T07:02:02Z

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Thursday, May 11, 2023 10:51 PM
>
> @@ -353,9 +353,64 @@ struct iommu_vfio_ioas {
> /**
> * enum iommu_hwpt_type - IOMMU HWPT Type
> * @IOMMU_HWPT_TYPE_DEFAULT: default
> + * @IOMMU_HWPT_TYPE_VTD_S1: Intel VT-d stage-1 page table
> */
> enum iommu_hwpt_type {
> IOMMU_HWPT_TYPE_DEFAULT,
> + IOMMU_HWPT_TYPE_VTD_S1,
> +};
> +
> +/**
> + * enum iommu_hwpt_intel_vtd_flags - Intel VT-d stage-1 page
> + * table entry attributes

No need to have both 'intel' and 'vtd' in one name. There won't
be another vtd. 😊

Also since it's for s1, let's be specific on the naming:

enum iommu_hwpt_vtd_s1_flags

> + * @IOMMU_VTD_PGTBL_SRE: Supervisor request
> + * @IOMMU_VTD_PGTBL_EAFE: Extended access enable
> + * @IOMMU_VTD_PGTBL_PCD: Page-level cache disable
> + * @IOMMU_VTD_PGTBL_PWT: Page-level write through
> + * @IOMMU_VTD_PGTBL_EMTE: Extended mem type enable
> + * @IOMMU_VTD_PGTBL_CD: PASID-level cache disable
> + * @IOMMU_VTD_PGTBL_WPE: Write protect enable

similarly above should be IOMMU_VTD_S1_SRE.

PGTBL can be skipped.

> + */
> +enum iommu_hwpt_intel_vtd_flags {
> + IOMMU_VTD_PGTBL_SRE = 1 << 0,
> + IOMMU_VTD_PGTBL_EAFE = 1 << 1,
> + IOMMU_VTD_PGTBL_PCD = 1 << 2,
> + IOMMU_VTD_PGTBL_PWT = 1 << 3,
> + IOMMU_VTD_PGTBL_EMTE = 1 << 4,
> + IOMMU_VTD_PGTBL_CD = 1 << 5,
> + IOMMU_VTD_PGTBL_WPE = 1 << 6,
> + IOMMU_VTD_PGTBL_LAST = 1 << 7,
> +};
> +
> +/**
> + * struct iommu_hwpt_intel_vtd - Intel VT-d specific user-managed
> + * stage-1 page table info

struct iommu_hwpt_vtd_s1

> + * @flags: Combination of enum iommu_hwpt_intel_vtd_flags
> + * @pgtbl_addr: The base address of the user-managed stage-1 page table.

no need to highlight 'user-managed' in every reference to stage-1

> + * @pat: Page attribute table data to compute effective memory type
> + * @emt: Extended memory type
> + * @addr_width: The address width of the untranslated addresses that are
> + * subjected to the user-managed stage-1 page table.

"The address width of the stage-1 page table"

> + * @__reserved: Must be 0
> + *
> + * The Intel VT-d specific data for creating hw_pagetable to represent
> + * the user-managed stage-1 page table that is used in nested translation.

"VT-d specific data for creating a stage-1 page table that ..."

> + *
> + * In nested translation, the stage-1 page table locates in the address
> + * space that defined by the corresponding stage-2 page table. Hence the

"locates in the address space of the specified stage-2 page table"

> + * stage-1 page table base address value should not be higher than the
> + * maximum untranslated address of stage-2 page table.

"should not exceed the maximum allowed input address of stage-2"

> + *
> + * The paging level of the stage-1 page table should be compatible with
> + * the hardware iommu. Otherwise, the allocation would be failed.

there is no information about paging level in this structure

> + */
> +struct iommu_hwpt_intel_vtd {
> + __u64 flags;
> + __u64 pgtbl_addr;
> + __u32 pat;
> + __u32 emt;
> + __u32 addr_width;
> + __u32 __reserved;
> };
>

I'd prefer to move vendor specific definitions before 'enum iommu_hwpt_type'
so any new added type can be easily correlated between the type enumeration
and following change in the comment of 'struct iommu_hwpt_alloc'

> /**
> @@ -391,6 +446,8 @@ enum iommu_hwpt_type {
> * +------------------------------+-------------------------------------+-----------+
> * | IOMMU_HWPT_TYPE_DEFAULT | N/A | IOAS |
> * +------------------------------+-------------------------------------+-----------+
> + * | IOMMU_HWPT_TYPE_VTD_S1 | struct iommu_hwpt_intel_vtd |
> HWPT |
> + * +------------------------------+-------------------------------------+-----------+
> */
> struct iommu_hwpt_alloc {
> __u32 size;
> --
> 2.34.1