Refactor memory access code; add MMIO support

Of course, it doesn't do anything yet.

1 files changed, 56 insertions, 47 deletions

diff --git a/riscv/mmu.cc b/riscv/mmu.cc
index cc21113..6173b43 100644
--- a/riscv/mmu.cc
+++ b/riscv/mmu.cc
@@ -29,55 +29,70 @@ void mmu_t::flush_tlb()
   flush_icache();
 }
 
-void* mmu_t::refill_tlb(reg_t addr, reg_t bytes, access_type type)
+reg_t mmu_t::translate(reg_t addr, access_type type)
 {
-  reg_t idx = (addr >> PGSHIFT) % TLB_ENTRIES;
-  reg_t expected_tag = addr >> PGSHIFT;
-
-  reg_t pgbase;
-  if (unlikely(!proc)) {
-    pgbase = addr & -PGSIZE;
-  } else {
-    reg_t mode = get_field(proc->state.mstatus, MSTATUS_PRV);
-    if (type != FETCH && get_field(proc->state.mstatus, MSTATUS_MPRV))
-      mode = get_field(proc->state.mstatus, MSTATUS_PRV1);
-    if (get_field(proc->state.mstatus, MSTATUS_VM) == VM_MBARE)
-      mode = PRV_M;
-  
-    if (mode == PRV_M) {
-      reg_t msb_mask = (reg_t(2) << (proc->xlen-1))-1; // zero-extend from xlen
-      pgbase = addr & -PGSIZE & msb_mask;
-    } else {
-      pgbase = walk(addr, mode > PRV_U, type);
-    }
+  if (!proc)
+    return addr;
+
+  reg_t mode = get_field(proc->state.mstatus, MSTATUS_PRV);
+  if (type != FETCH && get_field(proc->state.mstatus, MSTATUS_MPRV))
+    mode = get_field(proc->state.mstatus, MSTATUS_PRV1);
+  if (get_field(proc->state.mstatus, MSTATUS_VM) == VM_MBARE)
+    mode = PRV_M;
+
+  if (mode == PRV_M) {
+    reg_t msb_mask = (reg_t(2) << (proc->xlen-1))-1; // zero-extend from xlen
+    return addr & msb_mask;
   }
+  return walk(addr, mode > PRV_U, type) | (addr & (PGSIZE-1));
+}
 
-  reg_t pgoff = addr & (PGSIZE-1);
-  reg_t paddr = pgbase + pgoff;
+const uint16_t* mmu_t::fetch_slow_path(reg_t addr)
+{
+  reg_t paddr = translate(addr, FETCH);
+  if (paddr >= memsz)
+    throw trap_instruction_access_fault(addr);
+  return (const uint16_t*)(mem + paddr);
+}
 
-  if (pgbase >= memsz) {
-    if (type == FETCH) throw trap_instruction_access_fault(addr);
-    else if (type == STORE) throw trap_store_access_fault(addr);
-    else throw trap_load_access_fault(addr);
+void mmu_t::load_slow_path(reg_t addr, reg_t len, uint8_t* bytes)
+{
+  reg_t paddr = translate(addr, LOAD);
+  if (paddr < memsz) {
+    memcpy(bytes, mem + paddr, len);
+    if (!tracer.interested_in_range(paddr, paddr + PGSIZE, LOAD))
+      refill_tlb(addr, paddr, LOAD);
+  } else if (!proc || !proc->sim->mmio_load(addr, len, bytes)) {
+    throw trap_load_access_fault(addr);
   }
+}
 
-  bool trace = tracer.interested_in_range(pgbase, pgbase + PGSIZE, type);
-  if (unlikely(type != FETCH && trace))
-    tracer.trace(paddr, bytes, type);
-  else
-  {
-    if (tlb_load_tag[idx] != expected_tag) tlb_load_tag[idx] = -1;
-    if (tlb_store_tag[idx] != expected_tag) tlb_store_tag[idx] = -1;
-    if (tlb_insn_tag[idx] != expected_tag) tlb_insn_tag[idx] = -1;
+void mmu_t::store_slow_path(reg_t addr, reg_t len, const uint8_t* bytes)
+{
+  reg_t paddr = translate(addr, STORE);
+  if (paddr < memsz) {
+    memcpy(mem + paddr, bytes, len);
+    if (!tracer.interested_in_range(paddr, paddr + PGSIZE, STORE))
+      refill_tlb(addr, paddr, STORE);
+  } else if (!proc || !proc->sim->mmio_store(addr, len, bytes)) {
+    throw trap_store_access_fault(addr);
+  }
+}
+
+void mmu_t::refill_tlb(reg_t vaddr, reg_t paddr, access_type type)
+{
+  reg_t idx = (vaddr >> PGSHIFT) % TLB_ENTRIES;
+  reg_t expected_tag = vaddr >> PGSHIFT;
 
-    if (type == FETCH) tlb_insn_tag[idx] = expected_tag;
-    else if (type == STORE) tlb_store_tag[idx] = expected_tag;
-    else tlb_load_tag[idx] = expected_tag;
+  if (tlb_load_tag[idx] != expected_tag) tlb_load_tag[idx] = -1;
+  if (tlb_store_tag[idx] != expected_tag) tlb_store_tag[idx] = -1;
+  if (tlb_insn_tag[idx] != expected_tag) tlb_insn_tag[idx] = -1;
 
-    tlb_data[idx] = mem + pgbase - (addr & -PGSIZE);
-  }
+  if (type == FETCH) tlb_insn_tag[idx] = expected_tag;
+  else if (type == STORE) tlb_store_tag[idx] = expected_tag;
+  else tlb_load_tag[idx] = expected_tag;
 
-  return mem + paddr;
+  tlb_data[idx] = mem + paddr - vaddr;
 }
 
 reg_t mmu_t::walk(reg_t addr, bool supervisor, access_type type)
@@ -121,13 +136,7 @@ reg_t mmu_t::walk(reg_t addr, bool supervisor, access_type type)
       *(uint32_t*)ppte |= PTE_R | ((type == STORE) * PTE_D);
       // for superpage mappings, make a fake leaf PTE for the TLB's benefit.
       reg_t vpn = addr >> PGSHIFT;
-      reg_t addr = (ppn | (vpn & ((reg_t(1) << ptshift) - 1))) << PGSHIFT;
-
-      // check that physical address is legal
-      if (addr >= memsz)
-        break;
-
-      return addr;
+      return (ppn | (vpn & ((reg_t(1) << ptshift) - 1))) << PGSHIFT;
     }
   }