[PATCH v2 2/5] iommu: sun50i: allocate page tables from below 4 GiB

[Chen-Yu Tsai]

On Mon, Jun 17, 2024 at 6:42 AM Andre Przywara <andre.przywara at arm.com> wrote:
>
> The Allwinner IOMMU is a strict 32-bit device, with its input addresses,
> the page table root pointer as well as both level's page tables and also
> the target addresses all required to be below 4GB.
> The Allwinner H6 SoC only supports 32-bit worth of physical addresses
> anyway, so this isn't a problem so far, but the H616 and later SoCs extend
> the PA space beyond 32 bit to accommodate more DRAM.
> To make sure we stay within the 32-bit PA range required by the IOMMU,
> force the memory for the page tables to come from below 4GB. by using
> allocations with the DMA32 flag.
> Also reject any attempt to map target addresses beyond 4GB, and print a
> warning to give users a hint while this fails.
>
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>

Reviewed-by: Chen-Yu Tsai <wens at csie.org>

> ---
>  drivers/iommu/sun50i-iommu.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index dd3f07384624c..20a07f829085d 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -602,6 +602,14 @@ static int sun50i_iommu_map(struct iommu_domain *domain, unsigned long iova,
>         u32 *page_table, *pte_addr;
>         int ret = 0;
>
> +       /* the IOMMU can only handle 32-bit addresses, both input and output */
> +       if ((uint64_t)paddr >> 32) {
> +               ret = -EINVAL;
> +               dev_warn_once(iommu->dev,
> +                             "attempt to map address beyond 4GB\n");
> +               goto out;
> +       }
> +
>         page_table = sun50i_dte_get_page_table(sun50i_domain, iova, gfp);
>         if (IS_ERR(page_table)) {
>                 ret = PTR_ERR(page_table);
> @@ -682,7 +690,8 @@ sun50i_iommu_domain_alloc_paging(struct device *dev)
>         if (!sun50i_domain)
>                 return NULL;
>
> -       sun50i_domain->dt = iommu_alloc_pages(GFP_KERNEL, get_order(DT_SIZE));
> +       sun50i_domain->dt = iommu_alloc_pages(GFP_KERNEL | GFP_DMA32,
> +                                             get_order(DT_SIZE));
>         if (!sun50i_domain->dt)
>                 goto err_free_domain;
>
> @@ -997,7 +1006,7 @@ static int sun50i_iommu_probe(struct platform_device *pdev)
>
>         iommu->pt_pool = kmem_cache_create(dev_name(&pdev->dev),
>                                            PT_SIZE, PT_SIZE,
> -                                          SLAB_HWCACHE_ALIGN,
> +                                          SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA32,
>                                            NULL);
>         if (!iommu->pt_pool)
>                 return -ENOMEM;
> --
> 2.39.4
>