Hi Rob,
On Wed, Jun 26, 2024 at 01:40:26PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> Add an io-pgtable method to walk the pgtable returning the raw PTEs that
> would be traversed for a given iova access.
>
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
> drivers/iommu/io-pgtable-arm.c | 34 +++++++++++++++++++++++++---------
> include/linux/io-pgtable.h | 16 ++++++++++++++++
> 2 files changed, 41 insertions(+), 9 deletions(-)
Non-technical question, but with patch 2/2 being drm-specific, how do
you plan to get this merged this once it's finalised? I can take this
part via the IOMMU tree?
> +static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
> + unsigned long iova)
> +{
> + struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
> + struct io_pgtable_walk_data wd = {};
> + int ret, lvl;
> +
> + ret = arm_lpae_pgtable_walk(ops, iova, &wd);
> + if (ret)
> + return 0;
> +
> + lvl = wd.level + data->start_level;
nit, but the level is architectural so I think we should initialise
wd.level to data->start_level instead.
>
> -found_translation:
> iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1);
> - return iopte_to_paddr(pte, data) | iova;
> + return iopte_to_paddr(wd.ptes[wd.level - 1], data) | iova;
> }
>
> static void arm_lpae_restrict_pgsizes(struct io_pgtable_cfg *cfg)
> @@ -804,6 +819,7 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
> .map_pages = arm_lpae_map_pages,
> .unmap_pages = arm_lpae_unmap_pages,
> .iova_to_phys = arm_lpae_iova_to_phys,
> + .pgtable_walk = arm_lpae_pgtable_walk,
> };
>
> return data;
> diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> index 86cf1f7ae389..4d696724c7da 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -171,12 +171,26 @@ struct io_pgtable_cfg {
> };
> };
>
> +/**
> + * struct io_pgtable_walk_data - information from a pgtable walk
> + *
> + * @ptes: The recorded PTE values from the walk
> + * @level: The level of the last PTE
> + *
> + * @level also specifies the last valid index in @ptes
> + */
> +struct io_pgtable_walk_data {
> + u64 ptes[4];
> + int level;
> +};
I wonder if we can do better than hardcoding the '4' here? I wouldn't be
surprised if this doesn't work, but could we do something along the
lines of:
struct io_pgtable_walk_data {
int level;
int num_levels;
u64 ptes[] __counted_by(num_levels);
};
and then have the Arm (LPAE)-specific code wrap that in a private
structure:
struct arm_lpae_io_pgtable_walk_data {
struct io_pgtable_walk_data data;
u64 ptes[ARM_LPAE_MAX_LEVELS];
};
which is used by the walker?
Will
