+++ /dev/null
-from nmigen import Memory, Module, Signal
-from nmigen.cli import main
-from math import log
-
-class CacheWalker():
- """ The purpose of this module is to search a memory block given an
- associativity. This module will attempt to find a matching
- entry when given an address, and perform permission validation
- if successful.
- """
- def __init__(self, data_size, assoc, mem):
- """ Arguments:
- * data_size: (bit count) The size of the data words being processed
- * assoc: (int) The associativity of the memory to be parsed
- * mem: (nmigen.Memory) The memory to be parsed
-
- Return:
- 1. An entry was found -> Return PTE, set hit HIGH, set valid HIGH
- 2. An entry was NOT found -> set hit LOW, set valid HIGH
- 3. A permission fault occurs -> set hit LOW, set valid LOW
- """
- # Parameter parsing
- self.assoc = assoc # Assciativity of the cache
-
- self.read_port = mem.read_port
- self.write_port = mem.write_port
-
- if (mem_size % assoc != 0):
- print("Cache Walker: Memory cannot be distributed between sets")
-
- self.set_count = mem.depth / assoc # Number of sets in memory
- self.set_bit_count = log(set_count, 2) # Bit count for sets
- # Ensure set_bit_count is fully represented
- if(set_count % 2 != 0):
- set_bit_count += 1
-
- self.assoc_bits = Signal(set_bit_count) # Bits for associativity
-
- # Inputs
- self.vma = Signal(36) # Virtual Memory Address (VMA)
-
- # Output
- self.hit = Signal(1) # Denotes if the VMA had a mapped PTE
- self.pte = Signal(64) # PTE that was mapped to by the VMA
- self.valid = Signal(1) # Denotes if the permissions are correct