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

[Joe Komlodi]

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)) {
+            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 */
-- 
2.7.4