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rocket-chip/rocket/src/main/scala/tlb.scala
Andrew Waterman cc0f8962fb [rocket] take physical memory attribute check off critical path
Cache the attributes in the TLB instead.
2016-08-02 17:21:03 -07:00

186 lines
6.3 KiB
Scala

// See LICENSE for license details.
package rocket
import Chisel._
import Util._
import junctions._
import scala.math._
import cde.{Parameters, Field}
import uncore.agents.PseudoLRU
import uncore.coherence._
case object NTLBEntries extends Field[Int]
trait HasTLBParameters extends HasCoreParameters {
val entries = p(NTLBEntries)
val camAddrBits = log2Ceil(entries)
val camTagBits = asIdBits + vpnBits
}
class TLBReq(implicit p: Parameters) extends CoreBundle()(p) {
val vpn = UInt(width = vpnBitsExtended)
val passthrough = Bool()
val instruction = Bool()
val store = Bool()
}
class TLBResp(implicit p: Parameters) extends CoreBundle()(p) {
// lookup responses
val miss = Bool(OUTPUT)
val ppn = UInt(OUTPUT, ppnBits)
val xcpt_ld = Bool(OUTPUT)
val xcpt_st = Bool(OUTPUT)
val xcpt_if = Bool(OUTPUT)
val cacheable = Bool(OUTPUT)
}
class TLB(implicit val p: Parameters) extends Module with HasTLBParameters {
val io = new Bundle {
val req = Decoupled(new TLBReq).flip
val resp = new TLBResp
val ptw = new TLBPTWIO
}
val valid = Reg(init = UInt(0, entries))
val ppns = Reg(Vec(entries, UInt(width = ppnBits)))
val tags = Reg(Vec(entries, UInt(width = asIdBits + vpnBits)))
val s_ready :: s_request :: s_wait :: s_wait_invalidate :: Nil = Enum(UInt(), 4)
val state = Reg(init=s_ready)
val r_refill_tag = Reg(UInt(width = asIdBits + vpnBits))
val r_refill_waddr = Reg(UInt(width = log2Ceil(entries)))
val r_req = Reg(new TLBReq)
val do_mprv = io.ptw.status.mprv && !io.req.bits.instruction
val priv = Mux(do_mprv, io.ptw.status.mpp, io.ptw.status.prv)
val priv_s = priv === PRV.S
val priv_uses_vm = priv <= PRV.S && !io.ptw.status.debug
// share a single physical memory attribute checker (unshare if critical path)
val passthrough_ppn = io.req.bits.vpn(ppnBits-1, 0)
val refill_ppn = io.ptw.resp.bits.pte.ppn(ppnBits-1, 0)
val do_refill = Bool(usingVM) && io.ptw.resp.valid
val mpu_ppn = Mux(do_refill, refill_ppn, passthrough_ppn)
val prot = addrMap.getProt(mpu_ppn << pgIdxBits)
val cacheable = addrMap.isCacheable(mpu_ppn << pgIdxBits)
require(addrMap.flatten.forall { case (n, r) => (r.start | r.size) % (1 << pgIdxBits) == 0 })
val lookup_tag = Cat(io.ptw.ptbr.asid, io.req.bits.vpn(vpnBits-1,0))
val vm_enabled = Bool(usingVM) && io.ptw.status.vm(3) && priv_uses_vm && !io.req.bits.passthrough
val hitsVec = (0 until entries).map(i => valid(i) && vm_enabled && tags(i) === lookup_tag) :+ !vm_enabled
val hits = hitsVec.asUInt
// permission bit arrays
val pte_array = Reg(new PTE)
val u_array = Reg(UInt(width = entries)) // user permission
val sw_array = Reg(UInt(width = entries)) // write permission
val sx_array = Reg(UInt(width = entries)) // execute permission
val sr_array = Reg(UInt(width = entries)) // read permission
val xr_array = Reg(UInt(width = entries)) // read permission to executable page
val cash_array = Reg(UInt(width = entries)) // cacheable
val dirty_array = Reg(UInt(width = entries)) // PTE dirty bit
when (do_refill) {
val pte = io.ptw.resp.bits.pte
ppns(r_refill_waddr) := pte.ppn
tags(r_refill_waddr) := r_refill_tag
val mask = UIntToOH(r_refill_waddr)
valid := valid | mask
u_array := Mux(pte.u, u_array | mask, u_array & ~mask)
sw_array := Mux(pte.sw() && prot.w, sw_array | mask, sw_array & ~mask)
sx_array := Mux(pte.sx() && prot.x, sx_array | mask, sx_array & ~mask)
sr_array := Mux(pte.sr() && prot.r, sr_array | mask, sr_array & ~mask)
xr_array := Mux(pte.sx() && prot.r, xr_array | mask, xr_array & ~mask)
cash_array := Mux(cacheable, cash_array | mask, cash_array & ~mask)
dirty_array := Mux(pte.d, dirty_array | mask, dirty_array & ~mask)
}
val plru = new PseudoLRU(entries)
val repl_waddr = Mux(!valid.andR, PriorityEncoder(~valid), plru.replace)
val priv_ok = Mux(priv_s, ~Mux(io.ptw.status.pum, u_array, UInt(0)), u_array)
val w_array = Cat(prot.w, priv_ok & sw_array)
val x_array = Cat(prot.x, priv_ok & sx_array)
val r_array = Cat(prot.r, priv_ok & (sr_array | Mux(io.ptw.status.mxr, xr_array, UInt(0))))
val c_array = Cat(cacheable, cash_array)
val bad_va =
if (vpnBits == vpnBitsExtended) Bool(false)
else io.req.bits.vpn(vpnBits) =/= io.req.bits.vpn(vpnBits-1)
// it's only a store hit if the dirty bit is set
val tlb_hits = hits(entries-1, 0) & (dirty_array | ~Mux(io.req.bits.store, w_array, UInt(0)))
val tlb_hit = tlb_hits.orR
val tlb_miss = vm_enabled && !bad_va && !tlb_hit
when (io.req.valid && !tlb_miss) {
plru.access(OHToUInt(hits(entries-1, 0)))
}
io.req.ready := state === s_ready
io.resp.xcpt_ld := bad_va || (~r_array & hits).orR
io.resp.xcpt_st := bad_va || (~w_array & hits).orR
io.resp.xcpt_if := bad_va || (~x_array & hits).orR
io.resp.cacheable := (c_array & hits).orR
io.resp.miss := do_refill || tlb_miss
io.resp.ppn := Mux1H(hitsVec, ppns :+ passthrough_ppn)
io.ptw.req.valid := state === s_request
io.ptw.req.bits := io.ptw.status
io.ptw.req.bits.addr := r_refill_tag
io.ptw.req.bits.store := r_req.store
io.ptw.req.bits.fetch := r_req.instruction
if (usingVM) {
when (io.req.fire() && tlb_miss) {
state := s_request
r_refill_tag := lookup_tag
r_refill_waddr := repl_waddr
r_req := io.req.bits
}
when (state === s_request) {
when (io.ptw.invalidate) {
state := s_ready
}
when (io.ptw.req.ready) {
state := s_wait
when (io.ptw.invalidate) { state := s_wait_invalidate }
}
}
when (state === s_wait && io.ptw.invalidate) {
state := s_wait_invalidate
}
when (io.ptw.resp.valid) {
state := s_ready
}
when (io.ptw.invalidate) {
valid := 0
}
}
}
class DecoupledTLB(implicit p: Parameters) extends Module {
val io = new Bundle {
val req = Decoupled(new TLBReq).flip
val resp = Decoupled(new TLBResp)
val ptw = new TLBPTWIO
}
val reqq = Queue(io.req)
val tlb = Module(new TLB)
val resp_helper = DecoupledHelper(
reqq.valid, tlb.io.req.ready, io.resp.ready)
val tlb_miss = tlb.io.resp.miss
tlb.io.req.valid := resp_helper.fire(tlb.io.req.ready)
tlb.io.req.bits := reqq.bits
reqq.ready := resp_helper.fire(reqq.valid, !tlb_miss)
io.resp.valid := resp_helper.fire(io.resp.ready, !tlb_miss)
io.resp.bits := tlb.io.resp
io.ptw <> tlb.io.ptw
}