from nmigen.cli import main
from PermissionValidator import PermissionValidator
+from Cam import Cam
+from RegisterFile import RegisterFile
# The expected form of the data is
# Item (Bits)
# Tag (N - 79) / ASID (78 - 64) / PTE (63 - 0)
class TLB():
- def __init__(self):
+ def __init__(self, asid_size, vma_size, pte_size):
+ """ Arguments
+ * asid_size: Address Space IDentifier (ASID) typically 15 bits
+ * vma_size: Virtual Memory Address (VMA) typically 36 bits
+ * pte_size: Page Table Entry (PTE) typically 64 bits
+
+ Notes:
+ These arguments should represent the largest possible size
+ defined by the MODE settings. See
+ Volume II: RISC-V Privileged Architectures V1.10 Page 57
+ """
+
+ # Internal
+ self.state = 0
+ # L1 Cache Modules
+ L1_size = 8
+ bits_for_LRU = 8 # Just a placeholder for not. Arbitrary 8!
+ self.cam_L1 = Cam(vma_size, cam_size)
+ self.reg_file = RegisterFile(pte_size + bits_for_LRU, cam_size)
+
+ # Permission Validator
+ self.perm_validator = PermissionValidator(asid_size + pte_size)
+
# Inputs
self.super = Signal(1) # Supervisor Mode
self.super_access = Signal(1) # Supervisor Access
- self.command = Signal(2) # 00=None, 01=Search, 10=Write PTE, 11=Reset
+ self.command = Signal(2) # 00=None, 01=Search, 10=Write PTE, 11=None
self.xwr = Signal(3) # Execute, Write, Read
self.mode = Signal(4) # 4 bits for access to Sv48 on Rv64
- self.asid = Signal(15) # Address Space IDentifier (ASID)
- self.vma = Signal(36) # Virtual Memory Address (VMA)
- self.pte_in = Signal(64) # To be saved Page Table Entry (PTE)
+ self.asid = Signal(asid_size) # Address Space IDentifier (ASID)
+ self.vma = Signal(vma_size) # Virtual Memory Address (VMA)
+ self.pte_in = Signal(pte_size) # To be saved Page Table Entry (PTE)
# Outputs
self.hit = Signal(1) # Denotes if the VMA had a mapped PTE
- self.valid = Signal(1) # Denotes if the permissions are correct
- self.pteOut = Signal(64) # PTE that was mapped to by the VMA
-
- # Cam simulations
- mem_l1 = Memory(113, 32) # L1 TLB cache
- read_port_l1 = mem_l1.read_port
- write_port_l1 = mem_l1.write_port
-
- mem_l2 = Memory(113, 128) # L2 TLB cache
- read_port_l2 = mem_l2.read_port
- write_port_l2 = mem_l2.write_port
+ self.perm_valid = Signal(1) # Denotes if the permissions are correct
+ self.pte_out = Signal(pte_size) # PTE that was mapped to by the VMA
def elaborate(self, platform):
m = Module()
- m.d.submodules.perm_valid = perm_valid = PermissionValidator(113)
- m.d.sync += [
- Case(self.command, {
- # Search for PTE
- 1: [
- # Check first entry in set
- # TODO make module?
- read_port_l1.addr.eq(vma[0,2]),
- If(read_port_l1.data[0] == 1,
- perm_valid.data.eq(read_port_l1.data),
- perm_valid.xwr.eq(self.xwr),
- perm_valid.super.eq(self.super),
- perm_valid.super_access.eq(self.super_access),
- perm_valid.asid.eq(self.asid),
- self.valid,eq(perm_valid.valid)
- ),
- If(self.valid == 0,
- read_port_l1.addr.eq(vma[0,2] + 1),
- If(read_port_l1.data[0] == 1,
- perm_valid.data.eq(read_port_l1.data),
- perm_valid.xwr.eq(self.xwr),
- perm_valid.super.eq(self.super),
- perm_valid.super_access.eq(self.super_access),
- perm_valid.asid.eq(self.asid),
- self.valid,eq(perm_valid.valid)
- )
- )
- ]
- })
- ]
+
+ # Add submodules
+ m.d.submodules.perm_valididator += self.perm_validator
+ m.d.submodules.cam_L1 += self.cam_L1
+ m.d.sumbmodules.reg_file += self.reg_file
+
+ # When MODE specifies translation
+ # TODO add in different bit length handling ie prefix 0s
+ with m.If(self.mode != 0):
+ m.d.comb += [
+ self.cam_L1.enable.eq(1),
+ self.reg_file.enable.eq(1)
+ ]
+ with m.Switch(self.command):
+ # Search
+ with m.Case("01"):
+ m.d.comb += [
+ self.cam_L1.write_enable.eq(0),
+ self.cam_L1.data_in.eq(self.vma)
+ ]
+ # Write
+ with m.Case("10"):
+ # LRU logic should go in here
+ # Or take in address for writing?
+ # Add hardware option/software option
+ # SO MANY CHOICES
+ m.d.comb += [
+ self.cam_L1.write_enable.eq(1),
+ self.cam_L1.data_in.eq(self.vma)
+ ]
+ # Match found in L1 CAM
+ with m.If(self.cam_L1.single_match
+ | self.cam_L1.multiple_match):
+ # Register file shortcut variables
+ reg_addrress = self.cam_L1.match_address
+ reg_data = self.reg_file.register_array[reg_addrress]
+ # Set all permission validator fields
+ m.d.comb += [
+ self.hit.eq(1),
+ # Set permission validator data to the correct
+ # register file data according to CAM match
+ # address
+ self.perm_validator.data.eq(reg_data),
+ # Execute, Read, Write
+ self.perm_validator.xwr.eq(self.xwr),
+ # Supervisor Mode
+ self.perm_validator.super.eq(self.super),
+ # Supverisor Access
+ self.perm_validator.super_access.eq(self.super_access),
+ # Address Space IDentifier (ASID)
+ self.perm_validator.asid.eq(self.asid),
+ # Output result of permission validation
+ self.perm_valid.eq(self.perm_validator.valid)
+ ]
+ # Do not output PTE if permissions fail
+ with m.If(self.perm_validator.valid):
+ m.d.comb += [
+ self.pte_out.eq(reg_data)
+ ]
+ with m.Else():
+ m.d.comb += [
+ self.pte_out.eq(0)
+ ]
+ with m.Else():
+ m.d.comb += [
+ self.hit.eq(0),
+ self.perm_valid.eq(0),
+ self.pte_out.eq(0)
+ ]
+ # When disabled
+ with m.Else():
+ m.d.comb += [
+ self.cam_L1.enable.eq(0),
+ self.reg_file.enable.eq(0),
+ self.hit.eq(0),
+ self.valid.eq(0),
+ self.pte_out.eq(0)
+ ]
return m
thing = TLB()
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