[PATCH v7 05/15] iommupt: Add iova_to_phys op
Samiullah Khawaja
skhawaja at google.com
Mon Oct 27 09:51:16 PDT 2025
On Thu, Oct 23, 2025 at 11:21 AM Jason Gunthorpe <jgg at nvidia.com> wrote:
>
> iova_to_phys is a performance path for the DMA API and iommufd, implement
> it using an unrolled get_user_pages() like function waterfall scheme.
>
> The implementation itself is fairly trivial.
>
> Tested-by: Alejandro Jimenez <alejandro.j.jimenez at oracle.com>
> Reviewed-by: Kevin Tian <kevin.tian at intel.com>
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> ---
> drivers/iommu/generic_pt/iommu_pt.h | 105 ++++++++++++++++++++++++++++
> include/linux/generic_pt/iommu.h | 19 +++--
> 2 files changed, 119 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h
> index 564f2d3a6e11e1..5ff1b887928a46 100644
> --- a/drivers/iommu/generic_pt/iommu_pt.h
> +++ b/drivers/iommu/generic_pt/iommu_pt.h
> @@ -17,6 +17,111 @@
>
> #define DOMAIN_NS(op) CONCATENATE(CONCATENATE(pt_iommu_, PTPFX), op)
>
> +static int make_range_ul(struct pt_common *common, struct pt_range *range,
> + unsigned long iova, unsigned long len)
> +{
> + unsigned long last;
> +
> + if (unlikely(len == 0))
> + return -EINVAL;
> +
> + if (check_add_overflow(iova, len - 1, &last))
> + return -EOVERFLOW;
> +
> + *range = pt_make_range(common, iova, last);
> + if (sizeof(iova) > sizeof(range->va)) {
> + if (unlikely(range->va != iova || range->last_va != last))
> + return -EOVERFLOW;
> + }
> + return 0;
> +}
> +
> +static __maybe_unused int make_range_u64(struct pt_common *common,
> + struct pt_range *range, u64 iova,
> + u64 len)
> +{
> + if (unlikely(iova > ULONG_MAX || len > ULONG_MAX))
> + return -EOVERFLOW;
> + return make_range_ul(common, range, iova, len);
> +}
> +
> +/*
> + * Some APIs use unsigned long, while othersuse dma_addr_t as the type. Dispatch
> + * to the correct validation based on the type.
> + */
> +#define make_range_no_check(common, range, iova, len) \
> + ({ \
> + int ret; \
> + if (sizeof(iova) > sizeof(unsigned long) || \
> + sizeof(len) > sizeof(unsigned long)) \
> + ret = make_range_u64(common, range, iova, len); \
> + else \
> + ret = make_range_ul(common, range, iova, len); \
> + ret; \
> + })
> +
> +#define make_range(common, range, iova, len) \
> + ({ \
> + int ret = make_range_no_check(common, range, iova, len); \
> + if (!ret) \
> + ret = pt_check_range(range); \
> + ret; \
> + })
> +
> +static __always_inline int __do_iova_to_phys(struct pt_range *range, void *arg,
> + unsigned int level,
> + struct pt_table_p *table,
> + pt_level_fn_t descend_fn)
> +{
> + struct pt_state pts = pt_init(range, level, table);
> + pt_oaddr_t *res = arg;
> +
> + switch (pt_load_single_entry(&pts)) {
> + case PT_ENTRY_EMPTY:
> + return -ENOENT;
> + case PT_ENTRY_TABLE:
> + return pt_descend(&pts, arg, descend_fn);
> + case PT_ENTRY_OA:
> + *res = pt_entry_oa_exact(&pts);
> + return 0;
> + }
> + return -ENOENT;
> +}
> +PT_MAKE_LEVELS(__iova_to_phys, __do_iova_to_phys);
> +
> +/**
> + * iova_to_phys() - Return the output address for the given IOVA
> + * @iommu_table: Table to query
> + * @iova: IO virtual address to query
> + *
> + * Determine the output address from the given IOVA. @iova may have any
> + * alignment, the returned physical will be adjusted with any sub page offset.
> + *
> + * Context: The caller must hold a read range lock that includes @iova.
> + *
> + * Return: 0 if there is no translation for the given iova.
> + */
> +phys_addr_t DOMAIN_NS(iova_to_phys)(struct iommu_domain *domain,
> + dma_addr_t iova)
> +{
> + struct pt_iommu *iommu_table =
> + container_of(domain, struct pt_iommu, domain);
> + struct pt_range range;
> + pt_oaddr_t res;
> + int ret;
> +
> + ret = make_range(common_from_iommu(iommu_table), &range, iova, 1);
> + if (ret)
> + return ret;
> +
> + ret = pt_walk_range(&range, __iova_to_phys, &res);
> + /* PHYS_ADDR_MAX would be a better error code */
> + if (ret)
> + return 0;
> + return res;
> +}
> +EXPORT_SYMBOL_NS_GPL(DOMAIN_NS(iova_to_phys), "GENERIC_PT_IOMMU");
> +
> struct pt_iommu_collect_args {
> struct iommu_pages_list free_list;
> };
> diff --git a/include/linux/generic_pt/iommu.h b/include/linux/generic_pt/iommu.h
> index dc731fe003d153..5622856e199881 100644
> --- a/include/linux/generic_pt/iommu.h
> +++ b/include/linux/generic_pt/iommu.h
> @@ -116,11 +116,13 @@ struct pt_iommu_cfg {
> };
>
> /* Generate the exported function signatures from iommu_pt.h */
> -#define IOMMU_PROTOTYPES(fmt) \
> - int pt_iommu_##fmt##_init(struct pt_iommu_##fmt *table, \
> - const struct pt_iommu_##fmt##_cfg *cfg, \
> - gfp_t gfp); \
> - void pt_iommu_##fmt##_hw_info(struct pt_iommu_##fmt *table, \
> +#define IOMMU_PROTOTYPES(fmt) \
> + phys_addr_t pt_iommu_##fmt##_iova_to_phys(struct iommu_domain *domain, \
> + dma_addr_t iova); \
> + int pt_iommu_##fmt##_init(struct pt_iommu_##fmt *table, \
> + const struct pt_iommu_##fmt##_cfg *cfg, \
> + gfp_t gfp); \
> + void pt_iommu_##fmt##_hw_info(struct pt_iommu_##fmt *table, \
> struct pt_iommu_##fmt##_hw_info *info)
> #define IOMMU_FORMAT(fmt, member) \
> struct pt_iommu_##fmt { \
> @@ -129,6 +131,13 @@ struct pt_iommu_cfg {
> }; \
> IOMMU_PROTOTYPES(fmt)
>
> +/*
> + * A driver uses IOMMU_PT_DOMAIN_OPS to populate the iommu_domain_ops for the
> + * iommu_pt
> + */
> +#define IOMMU_PT_DOMAIN_OPS(fmt) \
> + .iova_to_phys = &pt_iommu_##fmt##_iova_to_phys,
> +
> /*
> * The driver should setup its domain struct like
> * union {
> --
> 2.43.0
>
>
Reviewed-by: Samiullah Khawaja <skhawaja at google.com>
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