On Sun, Mar 28, 2021 at 09:40:07AM +0200, Sven Peter wrote:
> Apple's DART iommu uses a pagetable format that shares some
> similarities with the ones already implemented by io-pgtable.c.
> Add a new format variant to support the required differences
> so that we don't have to duplicate the pagetable handling code.
>
> Signed-off-by: Sven Peter <s...@svenpeter.dev>
> ---
> drivers/iommu/io-pgtable-arm.c | 59 ++++++++++++++++++++++++++++++++++
> drivers/iommu/io-pgtable.c | 1 +
> include/linux/io-pgtable.h | 6 ++++
> 3 files changed, 66 insertions(+)
>
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 87def58e79b5..2f63443fd115 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -127,6 +127,9 @@
> #define ARM_MALI_LPAE_MEMATTR_IMP_DEF 0x88ULL
> #define ARM_MALI_LPAE_MEMATTR_WRITE_ALLOC 0x8DULL
>
> +#define APPLE_DART_PTE_PROT_NO_WRITE (1<<7)
> +#define APPLE_DART_PTE_PROT_NO_READ (1<<8)
> +
> /* IOPTE accessors */
> #define iopte_deref(pte,d) __va(iopte_to_paddr(pte, d))
>
> @@ -381,6 +384,15 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct
> arm_lpae_io_pgtable *data,
> {
> arm_lpae_iopte pte;
>
> + if (data->iop.fmt == ARM_APPLE_DART) {
> + pte = 0;
> + if (!(prot & IOMMU_WRITE))
> + pte |= APPLE_DART_PTE_PROT_NO_WRITE;
> + if (!(prot & IOMMU_READ))
> + pte |= APPLE_DART_PTE_PROT_NO_READ;
> + return pte;
> + }
> +
> if (data->iop.fmt == ARM_64_LPAE_S1 ||
> data->iop.fmt == ARM_32_LPAE_S1) {
> pte = ARM_LPAE_PTE_nG;
> @@ -1043,6 +1055,48 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg
> *cfg, void *cookie)
> return NULL;
> }
>
> +static struct io_pgtable *
> +apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
> +{
> + struct arm_lpae_io_pgtable *data;
> +
> + if (cfg->ias > 36)
> + return NULL;
> + if (cfg->oas > 36)
> + return NULL;
> +
> + if (!cfg->coherent_walk)
> + return NULL;
This all feels like IOMMU-specific limitations leaking into the page-table
code here; it doesn't feel so unlikely that future implementations of this
IP might have greater addressing capabilities, for example, and so I don't
see why the page-table code needs to police this.
> + cfg->pgsize_bitmap &= SZ_16K;
> + if (!cfg->pgsize_bitmap)
> + return NULL;
This is worrying (and again, I don't think this belongs here). How is this
thing supposed to work if the CPU is using 4k pages?
Will
