RE: [PATCH V4 04/10] iommufd: Add an ioctl IOMMU_IOAS_GET_PA to query PA from IOVA

[Tian, Kevin]

> From: Jacob Pan <jacob.pan@xxxxxxxxxxxxxxxxxxx>
> Sent: Wednesday, April 15, 2026 5:14 AM
> 
> To support no-IOMMU mode where userspace drivers perform unsafe DMA
> using physical addresses, introduce a new API to retrieve the
> physical address of a user-allocated DMA buffer that has been mapped to
> an IOVA via IOAS. The mapping is backed by mock I/O page tables
> maintained
> by generic IOMMUPT framework.
> 
> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.pan@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Your s-o-b should be the last 

> +	/*
> +	 * Scan the domain for the contiguous physical address length so that
> +	 * userspace search can be optimized for fewer ioctls.
> +	 */
> +	while (iova < iopt_area_last_iova(area)) {
> +		unsigned long next_iova;
> +		u64 next_paddr;
> +
> +		if (check_add_overflow(iova, PAGE_SIZE, &next_iova))
> +			break;
> +
> +		next_paddr = iommu_iova_to_phys(area->storage_domain,
> next_iova);
> +
> +		if (!next_paddr || next_paddr != tmp_paddr + PAGE_SIZE)
> +			break;

the 2nd condition should be WARN_ON? 

> @@ -432,6 +432,7 @@ union ucmd_buffer {
>  	struct iommu_veventq_alloc veventq;
>  	struct iommu_vfio_ioas vfio_ioas;
>  	struct iommu_viommu_alloc viommu;
> +	struct iommu_ioas_get_pa get_pa;

alphabetic order

>  #ifdef CONFIG_IOMMUFD_TEST
>  	struct iommu_test_cmd test;
>  #endif
> @@ -484,6 +485,8 @@ static const struct iommufd_ioctl_op
> iommufd_ioctl_ops[] = {
>  		 struct iommu_ioas_map_file, iova),
>  	IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct
> iommu_ioas_unmap,
>  		 length),
> +	IOCTL_OP(IOMMU_IOAS_GET_PA, iommufd_ioas_get_pa, struct
> iommu_ioas_get_pa,
> +		 out_phys),

ditto

> 
> +/**
> + * struct iommu_ioas_get_pa - ioctl(IOMMU_IOAS_GET_PA)
> + * @size: sizeof(struct iommu_ioas_get_pa)
> + * @flags: Reserved, must be 0 for now
> + * @ioas_id: IOAS ID to query IOVA to PA mapping from
> + * @__reserved: Must be 0
> + * @iova: IOVA to query
> + * @out_length: Number of bytes contiguous physical address starting from
> phys
> + * @out_phys: Output physical address the IOVA maps to
> + *
> + * Query the physical address backing an IOVA range. The entire range must
> be
> + * mapped already. For noiommu devices doing unsafe DMA only.
> + */
> +struct iommu_ioas_get_pa {
> +	__u32 size;
> +	__u32 flags;
> +	__u32 ioas_id;
> +	__u32 __reserved;
> +	__aligned_u64 iova;
> +	__aligned_u64 out_length;
> +	__aligned_u64 out_phys;
> +};
> +#define IOMMU_IOAS_GET_PA _IO(IOMMUFD_TYPE,
> IOMMUFD_CMD_IOAS_GET_PA)
> +

Based on its purpose let's make the restriction in the name, e.g.

IOMMUFD_CMD_IOAS_NOIOMMU_GET_PA