Re: [Qemu-devel] [RFC v4 1/5] hw/arm/smmu-common: smmu base class

[Peter Maydell <peter.maydell@linaro.org>]

On 13 May 2017 at 18:43, Eric Auger <eric.auger@redhat.com> wrote:
> Introduces the base device and class for the ARM smmu.
> Implements VMSAv8-64 table lookup and translation. VMSAv8-32
> is not yet implemented.
>
> For VFIO integration we will need to notify mapping changes
> of an input range and skipped unmapped regions. table walk
> helper allows.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
>
> +/**
> + * smmu_page_walk_level_64 - Walk an IOVA range from a specific level
> + * @baseaddr: table base address corresponding to @level
> + * @level: level
> + * @cfg: translation config
> + * @start: end of the IOVA range
> + * @end: end of the IOVA range
> + * @hook_fn: the hook that to be called for each detected area
> + * @private: private data for the hook function
> + * @read: whether parent level has read permission
> + * @write: whether parent level has write permission
> + * @must_translate: indicates whether each iova of the range
> + *  must be translated or whether failure is allowed
> + * @notify_unmap: whether we should notify invalid entries
> + *
> + * Return 0 on success, < 0 on errors not related to translation
> + * process, > 1 on errors related to translation process (only
> + * if must_translate is set)
> + */
> +static int
> +smmu_page_walk_level_64(dma_addr_t baseaddr, int level,
> +                        SMMUTransCfg *cfg, uint64_t start, uint64_t end,
> +                        smmu_page_walk_hook hook_fn, void *private,
> +                        bool read, bool write, bool must_translate,
> +                        bool notify_unmap)
> +{

> +        /* table pte */
> +        next_table_baseaddr = get_table_pte_address(pte, granule_sz);
> +        trace_smmu_page_walk_level_table_pte(pte, next_table_baseaddr);
> +        ret = smmu_page_walk_level_64(next_table_baseaddr, level + 1, cfg,
> +                                      iova, MIN(iova_next, end),
> +                                      hook_fn, private, read_cur, write_cur,
> +                                      must_translate, notify_unmap);
> +        if (!ret) {
> +            return ret;
> +        }
> +
> +next:
> +        iova = iova_next;
> +    }
> +
> +    return SMMU_TRANS_ERR_NONE;
> +}

It seems a bit odd that this function is recursive -- I was
expecting it just to loop through for each successive level
until it hits a block/page entry, as the LPAE table walk
code in target/arm/helper.c does...

thanks
-- PMM