+tlb_entry_t mmu_t::refill_tlb(reg_t vaddr, reg_t paddr, char* host_addr, access_type type)
+{
+ reg_t idx = (vaddr >> PGSHIFT) % TLB_ENTRIES;
+ reg_t expected_tag = vaddr >> PGSHIFT;
+
+ if ((tlb_load_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
+ tlb_load_tag[idx] = -1;
+ if ((tlb_store_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
+ tlb_store_tag[idx] = -1;
+ if ((tlb_insn_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
+ tlb_insn_tag[idx] = -1;
+
+ if ((check_triggers_fetch && type == FETCH) ||
+ (check_triggers_load && type == LOAD) ||
+ (check_triggers_store && type == STORE))
+ expected_tag |= TLB_CHECK_TRIGGERS;
+
+ 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;
+
+ tlb_entry_t entry = {host_addr - vaddr, paddr - vaddr};
+ tlb_data[idx] = entry;
+ return entry;
+}
+
+reg_t mmu_t::walk(reg_t addr, access_type type, reg_t mode)
+{
+ vm_info vm = decode_vm_info(proc->max_xlen, mode, proc->get_state()->satp);
+ if (vm.levels == 0)
+ return addr & ((reg_t(2) << (proc->xlen-1))-1); // zero-extend from xlen
+
+ bool s_mode = mode == PRV_S;
+ bool sum = get_field(proc->state.mstatus, MSTATUS_SUM);
+ bool mxr = get_field(proc->state.mstatus, MSTATUS_MXR);
+
+ // verify bits xlen-1:va_bits-1 are all equal
+ int va_bits = PGSHIFT + vm.levels * vm.idxbits;
+ reg_t mask = (reg_t(1) << (proc->xlen - (va_bits-1))) - 1;
+ reg_t masked_msbs = (addr >> (va_bits-1)) & mask;
+ if (masked_msbs != 0 && masked_msbs != mask)
+ vm.levels = 0;
+
+ reg_t base = vm.ptbase;
+ for (int i = vm.levels - 1; i >= 0; i--) {
+ int ptshift = i * vm.idxbits;
+ reg_t idx = (addr >> (PGSHIFT + ptshift)) & ((1 << vm.idxbits) - 1);
+
+ // check that physical address of PTE is legal
+ auto ppte = sim->addr_to_mem(base + idx * vm.ptesize);
+ if (!ppte)
+ goto fail_access;
+
+ reg_t pte = vm.ptesize == 4 ? *(uint32_t*)ppte : *(uint64_t*)ppte;
+ reg_t ppn = pte >> PTE_PPN_SHIFT;
+
+ if (PTE_TABLE(pte)) { // next level of page table
+ base = ppn << PGSHIFT;
+ } else if ((pte & PTE_U) ? s_mode && (type == FETCH || !sum) : !s_mode) {
+ break;
+ } else if (!(pte & PTE_V) || (!(pte & PTE_R) && (pte & PTE_W))) {
+ break;
+ } else if (type == FETCH ? !(pte & PTE_X) :
+ type == LOAD ? !(pte & PTE_R) && !(mxr && (pte & PTE_X)) :
+ !((pte & PTE_R) && (pte & PTE_W))) {
+ break;
+ } else if ((ppn & ((reg_t(1) << ptshift) - 1)) != 0) {
+ break;
+ } else {
+ reg_t ad = PTE_A | ((type == STORE) * PTE_D);
+#ifdef RISCV_ENABLE_DIRTY
+ // set accessed and possibly dirty bits.
+ *(uint32_t*)ppte |= ad;
+#else
+ // take exception if access or possibly dirty bit is not set.
+ if ((pte & ad) != ad)
+ break;
+#endif
+ // for superpage mappings, make a fake leaf PTE for the TLB's benefit.
+ reg_t vpn = addr >> PGSHIFT;
+ reg_t value = (ppn | (vpn & ((reg_t(1) << ptshift) - 1))) << PGSHIFT;
+ return value;