Add svnapot extention support

model/riscv_vmem.sail

@@ -45,6 +45,15 @@ function vpn_j_of_va(sv_params : SV_Params,
  ((va >> lsb) & mask)
 }
 
+// PRIVATE: Count trailing zeros
+function LowestSetBit(x : bits(64)) -> bits(64) = {
+ var count : bits(64) = zeros();
+ let perfect_one : bits(64) = 0x0000_0000_0000_0001;
+ foreach (i from 0 to (sizeof(xlen) - 1) by 1 in inc)
+ if [x[i]] == 0b1 then return(count + perfect_one) else (count = count + perfect_one);
+ return count;
+}
+
 // PRIVATE: Extract offset within page from VA
 function offset_of_va(va : bits(64)) -> bits(PAGESIZE_BITS) = va[pagesize_bits - 1 .. 0]
 
@@ -164,7 +173,28 @@ function pt_walk(sv_params,
  }
  }
  else {
+ let mask_bits = level * sv_params.pte_PPN_j_size_bits;
+ let mask : bits(64) = ~ (ones() << mask_bits);
+ let ppn : bits(64) = ppns | (vpns_of_va(sv_params, va) & mask);
+ let napot_bits = LowestSetBit(ppn);
+ let perfect_one : bits(64) = 0x0000_0000_0000_0001;
+ let napot_mask : bits(64) = (perfect_one << napot_bits) - perfect_one;
+ let napot_mask_not : bits(64) = ~ (napot_mask);
+ let ptshift_level = sv_params.levels - 1;
+ let ptshift = ptshift_level * sv_params.vpn_size_bits;
+
+ let page_base = (ppn & napot_mask_not) | 
+ (vpns_of_va(sv_params, va) & napot_mask) | 
+ (vpns_of_va(sv_params, va) & ((perfect_one << ptshift) - perfect_one));
+
  let pa = (ppns << pagesize_bits) | zero_extend(offset_of_va(va));
+ let pa_napot = page_base << 12 | zero_extend(offset_of_va(va));
+
+ // For svnapot ext purpose.
+ if (pte & (perfect_one << 63)) == (perfect_one << 63) then {
+ return PTW_Success(pa_napot, pte, pte_addr, level, global', ext_ptw)
+ };
+
  PTW_Success(pa, pte, pte_addr, level, global', ext_ptw)
  }
  }