mmu: add impl table and set function

some features are optional to u-arch or could be selectively supported.
Add an impl_table to keep implemented feature

Signed-off-by: Chih-Min Chao <chihmin.chao@sifive.com>

riscv/decode.h

@@ -236,6 +236,7 @@ private:
 #define require_rv64 require(xlen == 64)
 #define require_rv32 require(xlen == 32)
 #define require_extension(s) require(p->supports_extension(s))
+#define require_impl(s) require(p->supports_impl(s))
 #define require_fp require((STATE.mstatus & MSTATUS_FS) != 0)
 #define require_accelerator require((STATE.mstatus & MSTATUS_XS) != 0)
 

riscv/processor.cc

@@ -27,7 +27,7 @@ processor_t::processor_t(const char* isa, const char* priv, const char* varch,
   : debug(false), halt_request(HR_NONE), sim(sim), ext(NULL), id(id), xlen(0),
   histogram_enabled(false), log_commits_enabled(false),
   log_file(log_file), halt_on_reset(halt_on_reset),
-  extension_table(256, false), last_pc(1), executions(1)
+  extension_table(256, false), impl_table(256, false), last_pc(1), executions(1)
 {
   VU.p = this;
 
@@ -45,6 +45,12 @@ processor_t::processor_t(const char* isa, const char* priv, const char* varch,
 
   set_pmp_granularity(1 << PMP_SHIFT);
   set_pmp_num(state.max_pmp);
+
+  if (max_xlen == 32)
+    set_mmu_capability(IMPL_MMU_SV32);
+  else if (max_xlen == 64)
+    set_mmu_capability(IMPL_MMU_SV48);
+
   reset();
 }
 
@@ -502,6 +508,31 @@ void processor_t::set_pmp_granularity(reg_t gran) {
   lg_pmp_granularity = ctz(gran);
 }
 
+void processor_t::set_mmu_capability(int cap)
+{
+  switch (cap) {
+    case IMPL_MMU_SV32:
+      set_impl(cap, true);
+      set_impl(IMPL_MMU, true);
+      break;
+    case IMPL_MMU_SV39:
+      set_impl(cap, true);
+      set_impl(IMPL_MMU, true);
+      break;
+    case IMPL_MMU_SV48:
+      set_impl(cap, true);
+      set_impl(IMPL_MMU_SV39, true);
+      set_impl(IMPL_MMU, true);
+      break;
+    default:
+      set_impl(IMPL_MMU_SV32, false);
+      set_impl(IMPL_MMU_SV39, false);
+      set_impl(IMPL_MMU_SV48, false);
+      set_impl(IMPL_MMU, false);
+      break;
+  }
+}
+
 void processor_t::take_interrupt(reg_t pending_interrupts)
 {
   reg_t enabled_interrupts, deleg, status, mie, m_enabled;

riscv/processor.h

@@ -245,6 +245,14 @@ typedef enum {
   EXT_ZVEDIV,
 } isa_extension_t;
 
+typedef enum {
+  IMPL_MMU_SV32,
+  IMPL_MMU_SV39,
+  IMPL_MMU_SV48,
+  IMPL_MMU_BARE,
+  IMPL_MMU,
+} impl_extension_t;
+
 // Count number of contiguous 1 bits starting from the LSB.
 static int cto(reg_t val)
 {
@@ -292,6 +300,10 @@ public:
     else
       return extension_table[ext];
   }
+  void set_impl(uint8_t impl, bool val) { impl_table[impl] = val; }
+  bool supports_impl(uint8_t impl) const {
+    return impl_table[impl];
+  }
   reg_t pc_alignment_mask() {
     return ~(reg_t)(supports_extension('C') ? 0 : 2);
   }
@@ -409,6 +421,7 @@ public:
 
   void set_pmp_num(reg_t pmp_num);
   void set_pmp_granularity(reg_t pmp_granularity);
+  void set_mmu_capability(int cap);
 
   const char* get_symbol(uint64_t addr);
 
@@ -428,6 +441,7 @@ private:
   FILE *log_file;
   bool halt_on_reset;
   std::vector<bool> extension_table;
+  std::vector<bool> impl_table;
   
 
   std::vector<insn_desc_t> instructions;