TLB/src/ariane/ptw.py

   1 """
   2 # Copyright 2018 ETH Zurich and University of Bologna.
   3 # Copyright and related rights are licensed under the Solderpad Hardware
   4 # License, Version 0.51 (the "License"); you may not use this file except in
   5 # compliance with the License.  You may obtain a copy of the License at
   6 # http:#solderpad.org/licenses/SHL-0.51. Unless required by applicable law
   7 # or agreed to in writing, software, hardware and materials distributed under
   8 # this License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   9 # CONDITIONS OF ANY KIND, either express or implied. See the License for the
  10 # specific language governing permissions and limitations under the License.
  11 #
  12 # Author: David Schaffenrath, TU Graz
  13 # Author: Florian Zaruba, ETH Zurich
  14 # Date: 24.4.2017
  15 # Description: Hardware-PTW
  16
  17 /* verilator lint_off WIDTH */
  18 import ariane_pkg::*;
  19 """
  20
  21 from nmigen import Const, Signal
  22 from math import log
  23
  24 DCACHE_SET_ASSOC = 8
  25 CONFIG_L1D_SIZE =  32*1024
  26 DCACHE_INDEX_WIDTH = int(log(CONFIG_L1D_SIZE / DCACHE_SET_ASSOC))
  27 DCACHE_TAG_WIDTH = 56 - DCACHE_INDEX_WIDTH
  28
  29 class DCacheReqI:
  30     def __init__(self):
  31         self.address_index = Signal(DCACHE_INDEX_WIDTH)
  32         self.address_tag = Signal(DCACHE_TAG_WIDTH)
  33         self.data_wdata = Signal(64)
  34         self.data_req = Signal()
  35         self.data_we = Signal()
  36         self.data_be = Signal(8)
  37         self.data_size = Signal(2)
  38         self.kill_req = Signal()
  39         self.tag_valid = Signal()
  40
  41
  42 class DCacheReqO:
  43     def __init__(self):
  44         data_gnt = Signal()
  45         data_rvalid = Signal()
  46         data_rdata = Signal(64)
  47
  48 ASID_WIDTH = 1
  49
  50 class PTE: #(RecordObject):
  51     def __init__(self):
  52         self.reserved = Signal(10)
  53         self.ppn = Signal(44)
  54         self.rsw = Signal(2)
  55         self.d = Signal()
  56         self.a = Signal()
  57         self.g = Signal()
  58         self.u = Signal()
  59         self.x = Signal()
  60         self.w = Signal()
  61         self.r = Signal()
  62         self.v = Signal()
  63
  64     def eq(self, x):
  65         return [self.reserved.eq(x.reserved),
  66                 self.ppn.eq(x.ppn), self.rsw.eq(x.rsw),
  67                 self.d.eq(x.d), self.a.eq(x.a), self.g.eq(x.g),
  68                 self.u.eq(x.u), self.x.eq(x.x), self.w.eq(x.w),
  69                 self.r.eq(x.r), self.v.eq(x.v)]
  70
  71     def ports(self):
  72         return [self.reserved, self.ppn, self.rsw, self.d, self.a, self.g,
  73                 self.u, self.x, self.w, self.r, self.v]
  74
  75
  76 class TLBUpdate:
  77     def __init__(self):
  78         self.valid = Signal()      # valid flag
  79         self.is_2M = Signal()
  80         self.is_1G = Signal()
  81         self.vpn = Signal(27)
  82         self.asid = Signal(ASID_WIDTH)
  83         self.content = PTE()
  84
  85     def ports(self):
  86         return [self.valid, self.is_2M, self.is_1G, self.vpn, self.asid,
  87                 self.content.ports()]
  88
  89 # SV39 defines three levels of page tables
  90 LVL1 = Const(0, 2)
  91 LVL2 = Const(1, 2)
  92 LVL3 = Const(2, 2)
  93
  94
  95 class PTW:
  96     def __init__(self):
  97         flush_i = Signal() # flush everything, we need to do this because
  98         # actually everything we do is speculative at this stage
  99         # e.g.: there could be a CSR instruction that changes everything
 100         ptw_active_o = Signal()
 101         walking_instr_o = Signal()        # set when walking for TLB
 102         ptw_error_o = Signal()            # set when an error occurred
 103         enable_translation_i = Signal()   # CSRs indicate to enable SV39
 104         en_ld_st_translation_i = Signal() # enable VM translation for ld/st
 105
 106         lsu_is_store_i = Signal() ,       # this translation triggered by store
 107         # PTW memory interface
 108         req_port_i = DCacheReqO()
 109         req_port_o = DCacheReqI()
 110
 111         # to TLBs, update logic
 112         itlb_update_o = TLBUpdate()
 113         dtlb_update_o = TLBUpdate()
 114
 115         update_vaddr_o = Signal(39)
 116
 117         asid_i = Signal(ASID_WIDTH)
 118         # from TLBs
 119         # did we miss?
 120         itlb_access_i = Signal()
 121         itlb_hit_i = Signal()
 122         itlb_vaddr_i = Signal(64)
 123
 124         dtlb_access_i = Signal()
 125         dtlb_hit_i = Signal()
 126         dtlb_vaddr_i = Signal(64)
 127         # from CSR file
 128         satp_ppn_i = Signal(44) # ppn from satp
 129         mxr_i = Signal()
 130         # Performance counters
 131         itlb_miss_o = Signal()
 132         dtlb_miss_o = Signal()
 133
 134
 135         # input registers
 136         data_rvalid = Signal()
 137         data_rdata = Signal(64)
 138
 139         pte = PTE()
 140         m.d.comb += pte.eq(data_rdata)
 141
 142         ptw_lvl = Signal(2, reset=LVL1)
 143
 144         # is this an instruction page table walk?
 145         is_instr_ptw = Signal()
 146         global_mapping = Signal()
 147         # latched tag signal
 148         tag_valid = Signal()
 149         # register the ASID
 150         tlb_update_asid = Signal(ASID_WIDTH)
 151         # register the VPN we need to walk, SV39 defines a 39 bit virtual address
 152         vaddr = Signal(64)
 153         # 4 byte aligned physical pointer
 154         ptw_pptr = Signal(56)
 155
 156         end = DCACHE_INDEX_WIDTH + DCACHE_TAG_WIDTH
 157         m.d.sync += [
 158             # Assignments
 159             update_vaddr_o.eq(vaddr),
 160
 161             ptw_active_o.eq(state != IDLE),
 162             walking_instr_o.eq(is_instr_ptw),
 163             # directly output the correct physical address
 164             req_port_o.address_index.eq(ptw_pptr[0:DCACHE_INDEX_WIDTH]),
 165             req_port_o.address_tag.eq(ptw_pptr[DCACHE_INDEX_WIDTH:end]),
 166             # we are never going to kill this request
 167             req_port_o.kill_req.eq(0),
 168             # we are never going to write with the HPTW
 169             req_port_o.data_wdata.eq(Const(0, 64)),
 170             # -----------
 171             # TLB Update
 172             # -----------
 173             itlb_update_o.vpn.eq(vaddr[12:39]),
 174             dtlb_update_o.vpn.eq(vaddr[12:39]),
 175             # update the correct page table level
 176             itlb_update_o.is_2M.eq(ptw_lvl == LVL2),
 177             itlb_update_o.is_1G.eq(ptw_lvl == LVL1),
 178             dtlb_update_o.is_2M.eq(ptw_lvl == LVL2),
 179             dtlb_update_o.is_1G.eq(ptw_lvl == LVL1),
 180             # output the correct ASID
 181             itlb_update_o.asid.eq(tlb_update_asid),
 182             dtlb_update_o.asid.eq(tlb_update_asid),
 183             # set the global mapping bit
 184             itlb_update_o.content.eq(pte | (global_mapping << 5)),
 185             dtlb_update_o.content.eq(pte | (global_mapping << 5)),
 186
 187         ]
 188         m.d.comb += [
 189             req_port_o.tag_valid.eq(tag_valid),
 190         ]
 191         #-------------------
 192         # Page table walker
 193         #-------------------
 194         # A virtual address va is translated into a physical address pa as follows:
 195         # 1. Let a be sptbr.ppn × PAGESIZE, and let i = LEVELS-1. (For Sv39,
 196         #    PAGESIZE=2^12 and LEVELS=3.)
 197         # 2. Let pte be the value of the PTE at address a+va.vpn[i]×PTESIZE. (For
 198         #    Sv32, PTESIZE=4.)
 199         # 3. If pte.v = 0, or if pte.r = 0 and pte.w = 1, stop and raise an access
 200         #    exception.
 201         # 4. Otherwise, the PTE is valid. If pte.r = 1 or pte.x = 1, go to step 5.
 202         #    Otherwise, this PTE is a pointer to the next level of the page table.
 203         #    Let i=i-1. If i < 0, stop and raise an access exception. Otherwise, let
 204         #    a = pte.ppn × PAGESIZE and go to step 2.
 205         # 5. A leaf PTE has been found. Determine if the requested memory access
 206         #    is allowed by the pte.r, pte.w, and pte.x bits. If not, stop and
 207         #    raise an access exception. Otherwise, the translation is successful.
 208         #    Set pte.a to 1, and, if the memory access is a store, set pte.d to 1.
 209         #    The translated physical address is given as follows:
 210         #      - pa.pgoff = va.pgoff.
 211         #      - If i > 0, then this is a superpage translation and
 212         #        pa.ppn[i-1:0] = va.vpn[i-1:0].
 213         #      - pa.ppn[LEVELS-1:i] = pte.ppn[LEVELS-1:i].
 214         # 6. If i > 0 and pa.ppn[i − 1 : 0] != 0, this is a misaligned superpage;
 215         #    stop and raise a page-fault exception.
 216
 217         m.d.sync += tag_valid.eq(0)
 218
 219         # default assignments
 220         m.d.comb += [
 221             # PTW memory interface
 222             req_port_o.data_req.eq(0),
 223             req_port_o.data_be.eq(Const(0xFF, 8)),
 224             req_port_o.data_size.eq(Const(0b11, 2)),
 225             req_port_o.data_we.eq(0),
 226             ptw_error_o.eq(0),
 227             itlb_update_o.valid.eq(0),
 228             dtlb_update_o.valid.eq(0),
 229
 230             itlb_miss_o.eq(0),
 231             dtlb_miss_o.eq(0),
 232         ]
 233
 234         with m.FSM() as fsm:
 235
 236             with m.State("IDLE"):
 237                 # by default we start with the top-most page table
 238                 m.d.sync += [is_instr_ptw.eq(0),
 239                              ptw_lvl.eq(LVL1),
 240                              global_mapping.eq(0),
 241                             ]
 242                 # we got an ITLB miss?
 243                 with m.If(enable_translation_i & itlb_access_i & \
 244                           ~itlb_hit_i & ~dtlb_access_i):
 245                     pptr = Cat(Const(0, 3), itlb_vaddr_i[30:39], satp_ppn_i)
 246                     m.d.sync += [ptw_pptr.eq(pptr),
 247                                 is_instr_ptw.eq(1),
 248                                  vaddr.eq(itlb_vaddr_i),
 249                                 tlb_update_asid.eq(asid_i),
 250                                 ]
 251                     m.d.comb += [itlb_miss_o.eq(1)]
 252                     m.next = "WAIT_GRANT"
 253                 # we got a DTLB miss?
 254                 with m.Elif(en_ld_st_translation_i & dtlb_access_i & \
 255                             ~dtlb_hit_i):
 256                     pptr = Cat(Const(0, 3), dtlb_vaddr_i[30:39], satp_ppn_i)
 257                     m.d.sync += [ptw_pptr.eq(pptr),
 258                                  vaddr.eq(dtlb_vaddr_i),
 259                                  tlb_update_asid.eq(asid_i),
 260                                 ]
 261                     m.d.comb += [ dtlb_miss_o.eq(1)]
 262                     m.next = "WAIT_GRANT"
 263
 264             with m.State("WAIT_GRANT"):
 265                 # send a request out
 266                 m.d.comb += req_port_o.data_req.eq(1)
 267                 # wait for the WAIT_GRANT
 268                 with m.If(req_port_i.data_gnt):
 269                     # send the tag valid signal one cycle later
 270                     m.d.sync += tag_valid.eq(1)
 271                     m.next = "PTE_LOOKUP"
 272
 273             with m.State("PTE_LOOKUP"):
 274                 # we wait for the valid signal
 275                 with m.If(data_rvalid):
 276
 277                     # check if the global mapping bit is set
 278                     with m.If (pte.g):
 279                         m.d.sync += global_mapping.eq(1)
 280
 281                     # -------------
 282                     # Invalid PTE
 283                     # -------------
 284                     # If pte.v = 0, or if pte.r = 0 and pte.w = 1,
 285                     # stop and raise a page-fault exception.
 286                     with m.If (~pte.v | (~pte.r & pte.w)):
 287                         m.next = "PROPAGATE_ERROR"
 288                     # -----------
 289                     # Valid PTE
 290                     # -----------
 291                     with m.Else():
 292                         m.next = "IDLE"
 293                         # it is a valid PTE
 294                         # if pte.r = 1 or pte.x = 1 it is a valid PTE
 295                         with m.If (pte.r | pte.x):
 296                             # Valid translation found (either 1G, 2M or 4K entry)
 297                             with m.If(is_instr_ptw):
 298                                 # ------------
 299                                 # Update ITLB
 300                                 # ------------
 301                                 # If page is not executable, we can
 302                                 # directly raise an error. This
 303                                 # doesn't put a useless entry into
 304                                 # the TLB. The same idea applies
 305                                 # to the access flag since we let
 306                                 # the access flag be managed by SW.
 307                                 with m.If (~pte.x | ~pte.a):
 308                                     m.next = "IDLE"
 309                                 with m.Else():
 310                                     m.d.comb += itlb_update_o.valid.eq(1)
 311
 312                             with m.Else():
 313                                 # ------------
 314                                 # Update DTLB
 315                                 # ------------
 316                                 # Check if the access flag has been set,
 317                                 # otherwise throw a page-fault
 318                                 # and let the software handle those bits.
 319                                 # If page is not readable (there are
 320                                 # no write-only pages)
 321                                 # we can directly raise an error. This
 322                                 # doesn't put a useless
 323                                 # entry into the TLB.
 324                                 with m.If(pte.a & (pte.r | (pte.x & mxr_i))):
 325                                     m.d.comb += dtlb_update_o.valid.eq(1)
 326                                 with m.Else():
 327                                     m.next = "PROPAGATE_ERROR"
 328                                 # Request is a store: perform some
 329                                 # additional checks
 330                                 # If the request was a store and the
 331                                 # page is not write-able, raise an error
 332                                 # the same applies if the dirty flag is not set
 333                                 with m.If (lsu_is_store_i & (~pte.w | ~pte.d)):
 334                                     m.d.comb += dtlb_update_o.valid.eq(0)
 335                                     m.next = "PROPAGATE_ERROR"
 336
 337                             # check if the ppn is correctly aligned: Case (6)
 338                             l1err = Signal()
 339                             l2err = Signal()
 340                             m.d.comb += [l2err.eq((ptw_lvl == LVL2) & \
 341                                            pte.ppn[0:9] != Const(0, 9)),
 342                                          l1err.eq((ptw_lvl == LVL1) & \
 343                                            pte.ppn[0:18] != Const(0, 18))
 344                                         ]
 345                             with m.If(l1err | l2err):
 346                                 m.next = "PROPAGATE_ERROR"
 347                                 m.d.comb += [dtlb_update_o.valid.eq(0),
 348                                              itlb_update_o.valid.eq(0)]
 349
 350                         # this is a pointer to the next TLB level
 351                         with m.Else():
 352                             # pointer to next level of page table
 353                             with m.If (ptw_lvl == LVL1):
 354                                 # we are in the second level now
 355                                 pptr = Cat(Const(0, 3), dtlb_vaddr_i[21:30],
 356                                            pte.ppn)
 357                                 m.d.sync += [ptw_pptr.eq(pptr),
 358                                             ptw_lvl.eq(LVL2)]
 359                             with m.If(ptw_lvl == LVL2):
 360                                 # here we received a pointer to the third level
 361                                 pptr = Cat(Const(0, 3), dtlb_vaddr_i[12:21],
 362                                            pte.ppn)
 363                                 m.d.sync += [ptw_pptr.eq(pptr),
 364                                             ptw_lvl.eq(LVL3)
 365                                             ]
 366                             m.next = "WAIT_GRANT"
 367
 368                             with m.If (ptw_lvl == LVL3):
 369                                 # Should already be the last level
 370                                 # page table => Error
 371                                 m.d.sync += ptw_lvl.eq(LVL3)
 372                                 m.next = "PROPAGATE_ERROR"
 373                 # we've got a data WAIT_GRANT so tell the
 374                 # cache that the tag is valid
 375
 376             # Propagate error to MMU/LSU
 377             with m.State("PROPAGATE_ERROR"):
 378                 m.next = "IDLE"
 379                 m.d.comb += ptw_error_o.eq(1)
 380
 381             # wait for the rvalid before going back to IDLE
 382             with m.State("WAIT_RVALID"):
 383                 with m.If(data_rvalid):
 384                     m.next = "IDLE"
 385
 386         # -------
 387         # Flush
 388         # -------
 389         # should we have flushed before we got an rvalid,
 390         # wait for it until going back to IDLE
 391         with m.If(flush_i):
 392             # on a flush check whether we are
 393             # 1. in the PTE Lookup check whether we still need to wait
 394             #    for an rvalid
 395             # 2. waiting for a grant, if so: wait for it
 396             # if not, go back to idle
 397             with m.If (((state == PTE_LOOKUP) & ~data_rvalid) | \
 398                        ((state == WAIT_GRANT) & req_port_i.data_gnt)):
 399                 m.next = "WAIT_RVALID"
 400             with m.Else():
 401                 m.next = "IDLE"
 402
 403         m.d.sync += [data_rdata.eq(req_port_i.data_rdata),
 404                      data_rvalid.eq(req_port_i.data_rvalid)
 405                     ]
 406
 407 """
 408 if __name__ == '__main__':
 409     dut = PTE()
 410     ports = [dut.p.i_valid, dut.n.i_ready,
 411              dut.n.o_valid, dut.p.o_ready] + \
 412              [dut.p.i_data] + [dut.n.o_data]
 413     vl = rtlil.convert(dut, ports=ports)
 414     with open("test_bufunbuf999.il", "w") as f:
 415         f.write(vl)
 416 """