Re: [RFC V1 4/4] iommufd: update VA

[Jason Gunthorpe <jgg@nvidia.com>]

On Sat, Jul 20, 2024 at 11:56:45AM -0700, Steve Sistare wrote:
> @@ -458,6 +459,76 @@ static void change_mm(struct iopt_pages *pages)
>  	free_uid(old_user);
>  }
>  
> +#define MAX_UMAP_ENTRIES 1024

Only 170 of these fit in a 4k page :\

Are you worried about the high order allocation this could trigger?

I guess the alternative is to load it into a maple tree or similar,
but that is alot of memory allocations.

> +static int iommufd_get_umap(struct iommu_ioas_change_process *cmd,
> +			    struct iommu_ioas_userspace_map **p_umap)
> +{
> +	int i;
> +	int len = cmd->n_umap * sizeof(**p_umap);
> +	struct iommu_ioas_userspace_map *umap = kzalloc(len, GFP_KERNEL);
> +
> +	if (!umap)
> +		return -ENOMEM;
> +
> +	if (len > MAX_UMAP_ENTRIES * sizeof(*umap))
> +		return -E2BIG;
> +
> +	if (copy_from_user(umap, u64_to_user_ptr(cmd->umap), len)) {
> +		kfree(umap);
> +		return -EFAULT;
> +	}

This is memdup_user ?

> +struct iommu_ioas_userspace_map {
> +	__u64 addr_old;		/* old userspace virtual address */
> +	__u64 addr_new;		/* new userspace virtual address */
> +	__u64 size;		/* size of the mapping in bytes */
> +};

Use __aligned_u64 here as well

>  struct iommu_ioas_change_process {
>  	__u32 size;
> +	__u32 flags;
> +	__u32 n_umap;
> +	__u32 __reserved;
> +	__aligned_u64 umap;
>  };
> -
>  #define IOMMU_IOAS_CHANGE_PROCESS \
>  	_IO(IOMMUFD_TYPE, IOMMUFD_CMD_IOAS_CHANGE_PROCESS)
> -

These - lines should go in the prior patch

Jason