Re: [PATCH v3 4/6] hw/arm/smmuv3: Align stream table base address to table size

[Auger Eric <eric.auger@redhat.com>]

Hi Simon,

On 12/16/19 4:15 PM, Simon Veith wrote:
> Per the specification, and as observed in hardware, the SMMUv3 aligns
> the SMMU_STRTAB_BASE address to the size of the table by masking out the
> respective least significant bits in the ADDR field.
> 
> Apply this masking logic to our smmu_find_ste() lookup function per the
> specification.
> 
> ref. ARM IHI 0070C, section 6.3.23.
> 
> Signed-off-by: Simon Veith <sveith@amazon.de>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: qemu-devel@nongnu.org
> Cc: qemu-arm@nongnu.org
Looks good to me.

Acked-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
> Changed in v2:
> 
> * Now using MAKE_64BIT_MASK()
> * Eliminated unnecessary branches by using MAX()
> * Removed unnecessary range check against DMA_ADDR_BITS
> 
>  hw/arm/smmuv3.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index 727558b..31ac3ca 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -376,8 +376,9 @@ bad_ste:
>  static int smmu_find_ste(SMMUv3State *s, uint32_t sid, STE *ste,
>                           SMMUEventInfo *event)
>  {
> -    dma_addr_t addr;
> +    dma_addr_t addr, strtab_base;
>      uint32_t log2size;
> +    int strtab_size_shift;
>      int ret;
>  
>      trace_smmuv3_find_ste(sid, s->features, s->sid_split);
> @@ -391,10 +392,16 @@ static int smmu_find_ste(SMMUv3State *s, uint32_t sid, STE *ste,
>      }
>      if (s->features & SMMU_FEATURE_2LVL_STE) {
>          int l1_ste_offset, l2_ste_offset, max_l2_ste, span;
> -        dma_addr_t strtab_base, l1ptr, l2ptr;
> +        dma_addr_t l1ptr, l2ptr;
>          STEDesc l1std;
>  
> -        strtab_base = s->strtab_base & SMMU_BASE_ADDR_MASK;
> +        /*
> +         * Align strtab base address to table size. For this purpose, assume it
> +         * is not bounded by SMMU_IDR1_SIDSIZE.
> +         */
> +        strtab_size_shift = MAX(5, (int)log2size - s->sid_split - 1 + 3);
> +        strtab_base = s->strtab_base & SMMU_BASE_ADDR_MASK &
> +                      ~MAKE_64BIT_MASK(0, strtab_size_shift);
>          l1_ste_offset = sid >> s->sid_split;
>          l2_ste_offset = sid & ((1 << s->sid_split) - 1);
>          l1ptr = (dma_addr_t)(strtab_base + l1_ste_offset * sizeof(l1std));
> @@ -433,7 +440,10 @@ static int smmu_find_ste(SMMUv3State *s, uint32_t sid, STE *ste,
>          }
>          addr = l2ptr + l2_ste_offset * sizeof(*ste);
>      } else {
> -        addr = (s->strtab_base & SMMU_BASE_ADDR_MASK) + sid * sizeof(*ste);
> +        strtab_size_shift = log2size + 5;
> +        strtab_base = s->strtab_base & SMMU_BASE_ADDR_MASK &
> +                      ~MAKE_64BIT_MASK(0, strtab_size_shift);
> +        addr = strtab_base + sid * sizeof(*ste);
>      }
>  
>      if (smmu_get_ste(s, addr, ste, event)) {
>