Re: [PATCH 1/1] hw/arm/smmu: Add access flag handling

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

Hi Joe,

On 7/31/21 1:17 AM, Joe Komlodi wrote:
> The SMMU should access fault if AF == 0 in a TTD, and if AFFD == 0 in the CD.
>
> Per the spec, an access fault has a higher priority over a permission fault.
> For instance, a write to a writable clean (temporarily non-writable) page with
> AF == 0 && AFFD == 0 will cause an access fault.
> If AF == 1 in this situation, then a permission fault would occur.
>
> Access flag handling is more complicated if HTTU is supported and HA != 0 in
> the CD, however we currently do not support HTTU.
>
> Signed-off-by: Joe Komlodi <joe.komlodi@xilinx.com>
> ---
>  hw/arm/smmu-common.c         | 7 +++++++
>  hw/arm/smmu-internal.h       | 8 ++++++++
>  hw/arm/smmuv3-internal.h     | 1 +
>  hw/arm/smmuv3.c              | 1 +
>  include/hw/arm/smmu-common.h | 1 +
>  5 files changed, 18 insertions(+)
>
> diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
> index 0459850..0fcc65c 100644
> --- a/hw/arm/smmu-common.c
> +++ b/hw/arm/smmu-common.c
> @@ -305,6 +305,7 @@ static int smmu_ptw_64(SMMUTransCfg *cfg,
>          uint64_t pte, gpa;
>          dma_addr_t pte_addr = baseaddr + offset * sizeof(pte);
>          uint8_t ap;
> +        bool af;
>  
>          if (get_pte(baseaddr, offset, &pte, info)) {
>                  goto error;
> @@ -341,6 +342,12 @@ static int smmu_ptw_64(SMMUTransCfg *cfg,
>                                       pte_addr, pte, iova, gpa,
>                                       block_size >> 20);
>          }
> +        af = PTE_AF(pte);
> +        if (is_access_fault(af, perm)) {
I don't get the perm argument here.
 
Below there is this macro definition

+#define is_access_fault(af, cfg) \
+    (!cfg->affd && !af)

Thanks

Eric

> +            info->type = SMMU_PTW_ERR_ACCESS;
> +            goto error;
> +        }
> +
>          ap = PTE_AP(pte);
>          if (is_permission_fault(ap, perm)) {
>              info->type = SMMU_PTW_ERR_PERMISSION;
> diff --git a/hw/arm/smmu-internal.h b/hw/arm/smmu-internal.h
> index 2d75b31..9d3b22c 100644
> --- a/hw/arm/smmu-internal.h
> +++ b/hw/arm/smmu-internal.h
> @@ -58,6 +58,11 @@
>      ((level == 3) &&                                                    \
>       ((pte & ARM_LPAE_PTE_TYPE_MASK) == ARM_LPAE_L3_PTE_TYPE_PAGE))
>  
> +/* access flag */
> +
> +#define PTE_AF(pte) \
> +    (extract64(pte, 10, 1))
> +
>  /* access permissions */
>  
>  #define PTE_AP(pte) \
> @@ -66,6 +71,9 @@
>  #define PTE_APTABLE(pte) \
>      (extract64(pte, 61, 2))
>  
> +#define is_access_fault(af, cfg) \
> +    (!cfg->affd && !af)
> +
>  /*
>   * TODO: At the moment all transactions are considered as privileged (EL1)
>   * as IOMMU translation callback does not pass user/priv attributes.
> diff --git a/hw/arm/smmuv3-internal.h b/hw/arm/smmuv3-internal.h
> index d1885ae..0ccad1d 100644
> --- a/hw/arm/smmuv3-internal.h
> +++ b/hw/arm/smmuv3-internal.h
> @@ -587,6 +587,7 @@ static inline int pa_range(STE *ste)
>  #define CD_EPD(x, sel)   extract32((x)->word[0], (16 * (sel)) + 14, 1)
>  #define CD_ENDI(x)       extract32((x)->word[0], 15, 1)
>  #define CD_IPS(x)        extract32((x)->word[1], 0 , 3)
> +#define CD_AFFD(x)       extract32((x)->word[1], 3 , 1)
>  #define CD_TBI(x)        extract32((x)->word[1], 6 , 2)
>  #define CD_HD(x)         extract32((x)->word[1], 10 , 1)
>  #define CD_HA(x)         extract32((x)->word[1], 11 , 1)
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index 01b60be..df5a194 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -483,6 +483,7 @@ static int decode_cd(SMMUTransCfg *cfg, CD *cd, SMMUEventInfo *event)
>      cfg->oas = MIN(oas2bits(SMMU_IDR5_OAS), cfg->oas);
>      cfg->tbi = CD_TBI(cd);
>      cfg->asid = CD_ASID(cd);
> +    cfg->affd = CD_AFFD(cd);
>  
>      trace_smmuv3_decode_cd(cfg->oas);
>  
> diff --git a/include/hw/arm/smmu-common.h b/include/hw/arm/smmu-common.h
> index 706be3c..b0e82ad 100644
> --- a/include/hw/arm/smmu-common.h
> +++ b/include/hw/arm/smmu-common.h
> @@ -71,6 +71,7 @@ typedef struct SMMUTransCfg {
>      bool disabled;             /* smmu is disabled */
>      bool bypassed;             /* translation is bypassed */
>      bool aborted;              /* translation is aborted */
> +    bool affd;                 /* Access Flag Fault Disabled */
>      uint64_t ttb;              /* TT base address */
>      uint8_t oas;               /* output address width */
>      uint8_t tbi;               /* Top Byte Ignore */