[RFC PATCH v3 08/18] hw/arm/smmu-common: Add support for nested TLB

[Mostafa Saleh]

This patch adds support for nested(combined) TLB entries.
The main function combine_tlb() is not used here but in the next
patches, but to simplify the patches it is introduced first.

Main changes:
1) New entry added in the TLB, parent_perm, for nested TLB, holds the
   stage-2 permission, this can be used to know the origin of a
   permission fault from a cached entry as caching the “and” of the
   permissions loses this information.

   SMMUPTWEventInfo is used to hold information about PTW faults so
   the event can be populated, the value of stage (which maps to S2
   in the event) used to be set based on the current stage for TLB
   permission faults, however with the parent_perm, it is now set
   based on which perm has the missing permission

   When nesting is not enabled it has the same value as perm which
   doesn't change the logic.

2) As combined TLB implementation is used, the combination logic
   chooses:
   - tg and level from the entry which has the smallest addr_mask.
   - Based on that the iova that would be cached is recalculated.
   - Translated_addr is chosen from stage-2.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 hw/arm/smmu-common.c         | 32 ++++++++++++++++++++++++++++----
 include/hw/arm/smmu-common.h |  1 +
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
index 21982621c0..0d6945fa54 100644
--- a/hw/arm/smmu-common.c
+++ b/hw/arm/smmu-common.c
@@ -394,7 +394,7 @@ static int smmu_ptw_64_s1(SMMUTransCfg *cfg,
         tlbe->entry.translated_addr = gpa;
         tlbe->entry.iova = iova & ~mask;
         tlbe->entry.addr_mask = mask;
-        tlbe->entry.perm = PTE_AP_TO_PERM(ap);
+        tlbe->parent_perm = tlbe->entry.perm = PTE_AP_TO_PERM(ap);
         tlbe->level = level;
         tlbe->granule = granule_sz;
         return 0;
@@ -515,7 +515,7 @@ static int smmu_ptw_64_s2(SMMUTransCfg *cfg,
         tlbe->entry.translated_addr = gpa;
         tlbe->entry.iova = ipa & ~mask;
         tlbe->entry.addr_mask = mask;
-        tlbe->entry.perm = s2ap;
+        tlbe->parent_perm = tlbe->entry.perm = s2ap;
         tlbe->level = level;
         tlbe->granule = granule_sz;
         return 0;
@@ -530,6 +530,27 @@ error:
     return -EINVAL;
 }
 
+/* combine 2 TLB entries and return in tlbe in nested config. */
+static void __attribute__((unused)) combine_tlb(SMMUTLBEntry *tlbe,
+                                                SMMUTLBEntry *tlbe_s2,
+                                                dma_addr_t iova,
+                                                SMMUTransCfg *cfg)
+{
+    if (tlbe_s2->entry.addr_mask < tlbe->entry.addr_mask) {
+        tlbe->entry.addr_mask = tlbe_s2->entry.addr_mask;
+        tlbe->granule = tlbe_s2->granule;
+        tlbe->level = tlbe_s2->level;
+    }
+
+    tlbe->entry.translated_addr = CACHED_ENTRY_TO_ADDR(tlbe_s2,
+                                    tlbe->entry.translated_addr);
+
+    tlbe->entry.iova = iova & ~tlbe->entry.addr_mask;
+    /* parent_perm has s2 perm while perm has s1 perm. */
+    tlbe->parent_perm = tlbe_s2->entry.perm;
+    return;
+}
+
 /**
  * smmu_ptw - Walk the page tables for an IOVA, according to @cfg
  *
@@ -607,9 +628,12 @@ SMMUTLBEntry *smmu_translate(SMMUState *bs, SMMUTransCfg 
*cfg, dma_addr_t addr,
 
     cached_entry = smmu_iotlb_lookup(bs, cfg, &tt_combined, aligned_addr);
     if (cached_entry) {
-        if ((flag & IOMMU_WO) && !(cached_entry->entry.perm & IOMMU_WO)) {
+        if ((flag & IOMMU_WO) && !(cached_entry->entry.perm &
+            cached_entry->parent_perm & IOMMU_WO)) {
             info->type = SMMU_PTW_ERR_PERMISSION;
-            info->stage = cfg->stage;
+            info->stage = !(cached_entry->entry.perm & IOMMU_WO) ?
+                          SMMU_STAGE_1 :
+                          SMMU_STAGE_2;
             return NULL;
         }
         return cached_entry;
diff --git a/include/hw/arm/smmu-common.h b/include/hw/arm/smmu-common.h
index 09d3b9e734..1db566d451 100644
--- a/include/hw/arm/smmu-common.h
+++ b/include/hw/arm/smmu-common.h
@@ -77,6 +77,7 @@ typedef struct SMMUTLBEntry {
     IOMMUTLBEntry entry;
     uint8_t level;
     uint8_t granule;
+    IOMMUAccessFlags parent_perm;
 } SMMUTLBEntry;
 
 /* Stage-2 configuration. */
-- 
2.44.0.769.g3c40516874-goog