/* verilator lint_off WIDTH */
import ariane_pkg::*;
+
+see linux kernel source:
+
+* "arch/riscv/include/asm/page.h"
+* "arch/riscv/include/asm/mmu_context.h"
+* "arch/riscv/Kconfig" (CONFIG_PAGE_OFFSET)
+
"""
from nmigen import Const, Signal, Cat, Module
from nmigen.cli import verilog, rtlil
from math import log2
+
DCACHE_SET_ASSOC = 8
CONFIG_L1D_SIZE = 32*1024
DCACHE_INDEX_WIDTH = int(log2(CONFIG_L1D_SIZE / DCACHE_SET_ASSOC))
DCACHE_TAG_WIDTH = 56 - DCACHE_INDEX_WIDTH
+ASID_WIDTH = 8
+
class DCacheReqI:
def __init__(self):
def __init__(self):
self.data_gnt = Signal()
self.data_rvalid = Signal()
- self.data_rdata = Signal(64)
+ self.data_rdata = Signal(64) # actually in PTE object format
def ports(self):
return [ self.data_gnt, self.data_rvalid, self.data_rdata]
-ASID_WIDTH = 8
-
class PTE: #(RecordObject):
def __init__(self):
self.reserved = Signal(10)
return [self.valid, self.is_2M, self.is_1G, self.vpn, self.asid] + \
self.content.ports()
+
# SV39 defines three levels of page tables
LVL1 = Const(0, 2) # defined to 0 so that ptw_lvl default-resets to LVL1
LVL2 = Const(1, 2)
self.flush_i = Signal() # flush everything, we need to do this because
# actually everything we do is speculative at this stage
# e.g.: there could be a CSR instruction that changes everything
- self.ptw_active_o = Signal(reset=1)
+ self.ptw_active_o = Signal(reset=1) # active if not IDLE
self.walking_instr_o = Signal() # set when walking for TLB
self.ptw_error_o = Signal() # set when an error occurred
self.enable_translation_i = Signal() # CSRs indicate to enable SV39
data_rvalid = Signal()
data_rdata = Signal(64)
+ # NOTE: pte decodes the incoming bit-field (data_rdata). data_rdata
+ # is spec'd in 64-bit binary-format: better to spec as Record?
pte = PTE()
m.d.comb += pte.flatten().eq(data_rdata)
- ptw_lvl = Signal(2) # default=0=LVL1
-
- # used to continue checking flush conditions
- wait_grant = Signal()
+ # SV39 defines three levels of page tables
+ ptw_lvl = Signal(2) # default=0=LVL1 on reset (see above)
+ ptw_lvl1 = Signal()
+ ptw_lvl2 = Signal()
+ ptw_lvl3 = Signal()
+ m.d.comb += [ptw_lvl1.eq(ptw_lvl == LVL1),
+ ptw_lvl2.eq(ptw_lvl == LVL2),
+ ptw_lvl3.eq(ptw_lvl == LVL3)]
# is this an instruction page table walk?
is_instr_ptw = Signal()
self.req_port_o.address_index.eq(ptw_pptr[0:DCACHE_INDEX_WIDTH]),
self.req_port_o.address_tag.eq(ptw_pptr[DCACHE_INDEX_WIDTH:end]),
# we are never going to kill this request
- self.req_port_o.kill_req.eq(0),
+ self.req_port_o.kill_req.eq(0), # XXX assign comb?
# we are never going to write with the HPTW
- self.req_port_o.data_wdata.eq(Const(0, 64)),
+ self.req_port_o.data_wdata.eq(Const(0, 64)), # XXX assign comb?
# -----------
# TLB Update
# -----------
self.itlb_update_o.vpn.eq(vaddr[12:39]),
self.dtlb_update_o.vpn.eq(vaddr[12:39]),
# update the correct page table level
- self.itlb_update_o.is_2M.eq(ptw_lvl == LVL2),
- self.itlb_update_o.is_1G.eq(ptw_lvl == LVL1),
- self.dtlb_update_o.is_2M.eq(ptw_lvl == LVL2),
- self.dtlb_update_o.is_1G.eq(ptw_lvl == LVL1),
+ self.itlb_update_o.is_2M.eq(ptw_lvl2),
+ self.itlb_update_o.is_1G.eq(ptw_lvl1),
+ self.dtlb_update_o.is_2M.eq(ptw_lvl2),
+ self.dtlb_update_o.is_1G.eq(ptw_lvl1),
# output the correct ASID
self.itlb_update_o.asid.eq(tlb_update_asid),
self.dtlb_update_o.asid.eq(tlb_update_asid),
self.dtlb_update_o.content.eq(pte),
self.dtlb_update_o.content.g.eq(global_mapping),
- ]
- m.d.comb += [
self.req_port_o.tag_valid.eq(tag_valid),
]
+
#-------------------
# Page table walker
#-------------------
self.dtlb_miss_o.eq(0),
]
+ # ------------
+ # State Machine
+ # ------------
+
with m.FSM() as fsm:
with m.State("IDLE"):
- # by default we start with the top-most page table
- m.d.sync += [is_instr_ptw.eq(0),
- ptw_lvl.eq(LVL1),
- global_mapping.eq(0),
- self.ptw_active_o.eq(1),
- ]
- # we got an ITLB miss?
- with m.If(self.enable_translation_i & self.itlb_access_i & \
- ~self.itlb_hit_i & ~self.dtlb_access_i):
- pptr = Cat(Const(0, 3), self.itlb_vaddr_i[30:39], self.satp_ppn_i)
- m.d.sync += [ptw_pptr.eq(pptr),
- is_instr_ptw.eq(1),
- vaddr.eq(self.itlb_vaddr_i),
- tlb_update_asid.eq(self.asid_i),
- ]
- m.d.comb += [self.itlb_miss_o.eq(1)]
- self.set_grant_state(m)
- # we got a DTLB miss?
- with m.Elif(self.en_ld_st_translation_i & self.dtlb_access_i & \
- ~self.dtlb_hit_i):
- pptr = Cat(Const(0, 3), self.dtlb_vaddr_i[30:39], self.satp_ppn_i)
- m.d.sync += [ptw_pptr.eq(pptr),
- vaddr.eq(self.dtlb_vaddr_i),
- tlb_update_asid.eq(self.asid_i),
- ]
- m.d.comb += [ self.dtlb_miss_o.eq(1)]
- self.set_grant_state(m)
+ self.idle(m, is_instr_ptw, ptw_lvl, global_mapping,
+ ptw_pptr, vaddr, tlb_update_asid)
with m.State("WAIT_GRANT"):
- # send a request out
- m.d.comb += self.req_port_o.data_req.eq(1)
- # wait for the WAIT_GRANT
- with m.If(self.req_port_i.data_gnt):
- # send the tag valid signal one cycle later
- m.d.sync += tag_valid.eq(1)
- # should we have flushed before we got an rvalid,
- # wait for it until going back to IDLE
- with m.If(self.flush_i):
- with m.If (~data_rvalid):
- m.next = "WAIT_RVALID"
- with m.Else():
- m.next = "WAIT_RVALID"
- with m.Else():
- m.next = "PTE_LOOKUP"
+ self.grant(m, tag_valid, data_rvalid)
with m.State("PTE_LOOKUP"):
# we wait for the valid signal
with m.If(data_rvalid):
-
- # check if the global mapping bit is set
- with m.If (pte.g):
- m.d.sync += global_mapping.eq(1)
-
- # -------------
- # Invalid PTE
- # -------------
- # If pte.v = 0, or if pte.r = 0 and pte.w = 1,
- # stop and raise a page-fault exception.
- with m.If (~pte.v | (~pte.r & pte.w)):
- m.next = "PROPAGATE_ERROR"
- # -----------
- # Valid PTE
- # -----------
- with m.Else():
- m.next = "IDLE"
- # it is a valid PTE
- # if pte.r = 1 or pte.x = 1 it is a valid PTE
- with m.If (pte.r | pte.x):
- # Valid translation found (either 1G, 2M or 4K entry)
- with m.If(is_instr_ptw):
- # ------------
- # Update ITLB
- # ------------
- # If page is not executable, we can
- # directly raise an error. This
- # doesn't put a useless entry into
- # the TLB. The same idea applies
- # to the access flag since we let
- # the access flag be managed by SW.
- with m.If (~pte.x | ~pte.a):
- m.next = "IDLE"
- with m.Else():
- m.d.comb += self.itlb_update_o.valid.eq(1)
-
- with m.Else():
- # ------------
- # Update DTLB
- # ------------
- # Check if the access flag has been set,
- # otherwise throw a page-fault
- # and let the software handle those bits.
- # If page is not readable (there are
- # no write-only pages)
- # we can directly raise an error. This
- # doesn't put a useless
- # entry into the TLB.
- with m.If(pte.a & (pte.r | (pte.x & self.mxr_i))):
- m.d.comb += self.dtlb_update_o.valid.eq(1)
- with m.Else():
- m.next = "PROPAGATE_ERROR"
- # Request is a store: perform some
- # additional checks
- # If the request was a store and the
- # page is not write-able, raise an error
- # the same applies if the dirty flag is not set
- with m.If (self.lsu_is_store_i & (~pte.w | ~pte.d)):
- m.d.comb += self.dtlb_update_o.valid.eq(0)
- m.next = "PROPAGATE_ERROR"
-
- # check if the ppn is correctly aligned: Case (6)
- l1err = Signal()
- l2err = Signal()
- m.d.comb += [l2err.eq((ptw_lvl == LVL2) & \
- pte.ppn[0:9] != Const(0, 9)),
- l1err.eq((ptw_lvl == LVL1) & \
- pte.ppn[0:18] != Const(0, 18))
- ]
- with m.If(l1err | l2err):
- m.next = "PROPAGATE_ERROR"
- m.d.comb += [self.dtlb_update_o.valid.eq(0),
- self.itlb_update_o.valid.eq(0)]
-
- # this is a pointer to the next TLB level
- with m.Else():
- # pointer to next level of page table
- with m.If (ptw_lvl == LVL1):
- # we are in the second level now
- pptr = Cat(Const(0, 3), self.dtlb_vaddr_i[21:30],
- pte.ppn)
- m.d.sync += [ptw_pptr.eq(pptr),
- ptw_lvl.eq(LVL2)]
- with m.If(ptw_lvl == LVL2):
- # here we received a pointer to the third level
- pptr = Cat(Const(0, 3), self.dtlb_vaddr_i[12:21],
- pte.ppn)
- m.d.sync += [ptw_pptr.eq(pptr),
- ptw_lvl.eq(LVL3)
- ]
- self.set_grant_state(m)
-
- with m.If (ptw_lvl == LVL3):
- # Should already be the last level
- # page table => Error
- m.d.sync += ptw_lvl.eq(LVL3)
- m.d.comb += wait_grant.eq(0)
- m.next = "PROPAGATE_ERROR"
- # we've got a data WAIT_GRANT so tell the
- # cache that the tag is valid
+ self.lookup(m, pte, ptw_lvl, ptw_lvl1, ptw_lvl2, ptw_lvl3,
+ data_rvalid, global_mapping,
+ is_instr_ptw, ptw_pptr)
# Propagate error to MMU/LSU
with m.State("PROPAGATE_ERROR"):
with m.Else():
m.next = "WAIT_GRANT"
+ def idle(self, m, is_instr_ptw, ptw_lvl, global_mapping,
+ ptw_pptr, vaddr, tlb_update_asid):
+ # by default we start with the top-most page table
+ m.d.sync += [is_instr_ptw.eq(0),
+ ptw_lvl.eq(LVL1),
+ global_mapping.eq(0),
+ self.ptw_active_o.eq(0), # deactive (IDLE)
+ ]
+ # work out itlb/dtlb miss
+ m.d.comb += self.itlb_miss_o.eq(self.enable_translation_i & \
+ self.itlb_access_i & \
+ ~self.itlb_hit_i & \
+ ~self.dtlb_access_i)
+ m.d.comb += self.dtlb_miss_o.eq(self.en_ld_st_translation_i & \
+ self.dtlb_access_i & \
+ ~self.dtlb_hit_i)
+ # we got an ITLB miss?
+ with m.If(self.itlb_miss_o):
+ pptr = Cat(Const(0, 3), self.itlb_vaddr_i[30:39],
+ self.satp_ppn_i)
+ m.d.sync += [ptw_pptr.eq(pptr),
+ is_instr_ptw.eq(1),
+ vaddr.eq(self.itlb_vaddr_i),
+ tlb_update_asid.eq(self.asid_i),
+ ]
+ self.set_grant_state(m)
+
+ # we got a DTLB miss?
+ with m.Elif(self.dtlb_miss_o):
+ pptr = Cat(Const(0, 3), self.dtlb_vaddr_i[30:39],
+ self.satp_ppn_i)
+ m.d.sync += [ptw_pptr.eq(pptr),
+ vaddr.eq(self.dtlb_vaddr_i),
+ tlb_update_asid.eq(self.asid_i),
+ ]
+ self.set_grant_state(m)
+
+ def grant(self, m, tag_valid, data_rvalid):
+ # we've got a data WAIT_GRANT so tell the
+ # cache that the tag is valid
+
+ # send a request out
+ m.d.comb += self.req_port_o.data_req.eq(1)
+ # wait for the WAIT_GRANT
+ with m.If(self.req_port_i.data_gnt):
+ # send the tag valid signal one cycle later
+ m.d.sync += tag_valid.eq(1)
+ # should we have flushed before we got an rvalid,
+ # wait for it until going back to IDLE
+ with m.If(self.flush_i):
+ with m.If (~data_rvalid):
+ m.next = "WAIT_RVALID"
+ with m.Else():
+ m.next = "IDLE"
+ with m.Else():
+ m.next = "PTE_LOOKUP"
+
+ def lookup(self, m, pte, ptw_lvl, ptw_lvl1, ptw_lvl2, ptw_lvl3,
+ data_rvalid, global_mapping,
+ is_instr_ptw, ptw_pptr):
+ # temporaries
+ pte_rx = Signal(reset_less=True)
+ pte_exe = Signal(reset_less=True)
+ pte_inv = Signal(reset_less=True)
+ pte_a = Signal(reset_less=True)
+ st_wd = Signal(reset_less=True)
+ m.d.comb += [pte_rx.eq(pte.r | pte.x),
+ pte_exe.eq(~pte.x | ~pte.a),
+ pte_inv.eq(~pte.v | (~pte.r & pte.w)),
+ pte_a.eq(pte.a & (pte.r | (pte.x & self.mxr_i))),
+ st_wd.eq(self.lsu_is_store_i & (~pte.w | ~pte.d))]
+
+ l1err = Signal(reset_less=True)
+ l2err = Signal(reset_less=True)
+ m.d.comb += [l2err.eq((ptw_lvl2) & pte.ppn[0:9] != Const(0, 9)),
+ l1err.eq((ptw_lvl1) & pte.ppn[0:18] != Const(0, 18)) ]
+
+ # check if the global mapping bit is set
+ with m.If (pte.g):
+ m.d.sync += global_mapping.eq(1)
+
+ m.next = "IDLE"
+
+ # -------------
+ # Invalid PTE
+ # -------------
+ # If pte.v = 0, or if pte.r = 0 and pte.w = 1,
+ # stop and raise a page-fault exception.
+ with m.If (pte_inv):
+ m.next = "PROPAGATE_ERROR"
+
+ # -----------
+ # Valid PTE
+ # -----------
+
+ # it is a valid PTE
+ # if pte.r = 1 or pte.x = 1 it is a valid PTE
+ with m.Elif (pte_rx):
+ # Valid translation found (either 1G, 2M or 4K)
+ with m.If(is_instr_ptw):
+ # ------------
+ # Update ITLB
+ # ------------
+ # If page not executable, we can directly raise error.
+ # This doesn't put a useless entry into the TLB.
+ # The same idea applies to the access flag since we let
+ # the access flag be managed by SW.
+ with m.If (pte_exe):
+ m.next = "IDLE"
+ with m.Else():
+ m.d.comb += self.itlb_update_o.valid.eq(1)
+
+ with m.Else():
+ # ------------
+ # Update DTLB
+ # ------------
+ # Check if the access flag has been set, otherwise
+ # throw page-fault and let software handle those bits.
+ # If page not readable (there are no write-only pages)
+ # directly raise an error. This doesn't put a useless
+ # entry into the TLB.
+ with m.If(pte_a):
+ m.d.comb += self.dtlb_update_o.valid.eq(1)
+ with m.Else():
+ m.next = "PROPAGATE_ERROR"
+ # Request is a store: perform additional checks
+ # If the request was a store and the page not
+ # write-able, raise an error
+ # the same applies if the dirty flag is not set
+ with m.If (st_wd):
+ m.d.comb += self.dtlb_update_o.valid.eq(0)
+ m.next = "PROPAGATE_ERROR"
+
+ # check if the ppn is correctly aligned: Case (6)
+ with m.If(l1err | l2err):
+ m.next = "PROPAGATE_ERROR"
+ m.d.comb += [self.dtlb_update_o.valid.eq(0),
+ self.itlb_update_o.valid.eq(0)]
+
+ # this is a pointer to the next TLB level
+ with m.Else():
+ # pointer to next level of page table
+ with m.If (ptw_lvl1):
+ # we are in the second level now
+ pptr = Cat(Const(0, 3), self.dtlb_vaddr_i[21:30], pte.ppn)
+ m.d.sync += [ptw_pptr.eq(pptr),
+ ptw_lvl.eq(LVL2)
+ ]
+ with m.If(ptw_lvl2):
+ # here we received a pointer to the third level
+ pptr = Cat(Const(0, 3), self.dtlb_vaddr_i[12:21], pte.ppn)
+ m.d.sync += [ptw_pptr.eq(pptr),
+ ptw_lvl.eq(LVL3)
+ ]
+ self.set_grant_state(m)
+
+ with m.If (ptw_lvl3):
+ # Should already be the last level
+ # page table => Error
+ m.d.sync += ptw_lvl.eq(LVL3)
+ m.next = "PROPAGATE_ERROR"
+
if __name__ == '__main__':
ptw = PTW()
projects / soc.git / blobdiff