Re: [RFC PATCH 07/16] hw/arm/smmuv3: Check validity of stage-2 page table

[Eric Auger]

Hi Mostafa,
On 2/5/23 10:44, Mostafa Saleh wrote:
> Check if with the configured start level, ia_bits and granularity we
> can have a valid page table as described in ARM ARM D8.2 Translation
> process.
> The idea is to see for the highest possible number of IPA bits, how
> many concatenated tables we would need, if it is more than 16, then
> this is not possible.

This rather checks the validity and consistency of the STE S2 fields.
The patch title sounds a bit misleading to me.
>
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> ---
>  hw/arm/smmuv3.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index 6633fe40fa..c49b341287 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -341,6 +341,28 @@ static int smmu_get_cd(SMMUv3State *s, STE *ste, 
> uint32_t ssid,
>      return 0;
>  }
>  
> +/*
> + * Return true if s2 page table config is valid.
> + * This checks with the configured start level, ia_bits and granularity we 
> can
> + * have a valid page table as described in ARM ARM D8.2 Translation process.
> + * The idea here is to see for the highest possible number of IPA bits, how
> + * many concatenated tables we would need, if it is more than 16, then this 
> is
> + * not possible.
> + */
> +static bool s2_pgtable_config_valid(uint8_t sl0, uint8_t t0sz, uint8_t gran)
> +{
> +    int level = get_start_level(sl0, gran);
> +    uint64_t ia_bits = 64 - t0sz;
s/ia/ipa
> +    uint64_t mx = (1ULL << ia_bits) - 1;
s/mx/max_ipa
> +    int nr_concat = pgd_idx(level, gran, mx) + 1;
> +
> +    if (nr_concat > SMMU_MAX_S2_CONCAT) {
> +        return false;
> +    }
> +
> +    return true;
> +}
> +
>  /* Returns < 0 in case of invalid STE, 0 otherwise */
>  static int decode_ste(SMMUv3State *s, SMMUTransCfg *cfg,
>                        STE *ste, SMMUEventInfo *event)
> @@ -407,6 +429,13 @@ static int decode_ste(SMMUv3State *s, SMMUTransCfg *cfg,
>              goto bad_ste;
>          }
>  
> +        if (!s2_pgtable_config_valid(cfg->s2cfg.sl0, cfg->s2cfg.tsz,
> +                                     cfg->s2cfg.granule_sz)) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "SMMUv3 STE stage 2 config not valid!\n");
> +            goto bad_ste;
> +        }
> +
To me this would need to be integrated into the STE decoding patch. This
latter shall be self-contained if possible to ease the review

Thanks

Eric
>          /* This is still here as stage 2 has not been fully enabled yet. */
>          qemu_log_mask(LOG_UNIMP, "SMMUv3 does not support stage 2 yet\n");
>          goto bad_ste;