riscv/rocket-chip
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Zap conflicting TLB entries, preparing for superpage support

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Superpages create the possibility that two entries in the TLB may match.
This corresponds to a software bug, but we can't return complete garbage;
we must return either the old translation or the new translation.  This
isn't compatible with the Mux1H approach.  So, flush the TLB and report
a miss on duplicate entries.
This commit is contained in:
Andrew Waterman 2017-03-10 14:00:36 -08:00
parent b24c43badb
commit 380c10f7bd
1 changed files with 9 additions and 2 deletions
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11
src/main/scala/rocket/TLB.scala
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@ -132,12 +132,19 @@ class TLB(entries: Int)(implicit edge: TLEdgeOut, p: Parameters) extends CoreMod
plru.access(OHToUInt(hits(entries-1, 0))) plru.access(OHToUInt(hits(entries-1, 0)))
} }
// Superpages create the possibility that two entries in the TLB may match.
// This corresponds to a software bug, but we can't return complete garbage;
// we must return either the old translation or the new translation. This
// isn't compatible with the Mux1H approach. So, flush the TLB and report
// a miss on duplicate entries.
val multipleHits = PopCountAtLeast(hits(entries-1, 0), 2)
io.req.ready := state === s_ready io.req.ready := state === s_ready
io.resp.xcpt_ld := bad_va || (~r_array & hits).orR io.resp.xcpt_ld := bad_va || (~r_array & hits).orR
io.resp.xcpt_st := bad_va || (~w_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.xcpt_if := bad_va || (~x_array & hits).orR
io.resp.cacheable := (c_array & hits).orR io.resp.cacheable := (c_array & hits).orR
io.resp.miss := do_refill || tlb_miss io.resp.miss := do_refill || tlb_miss || multipleHits
io.resp.ppn := Mux1H(hitsVec, ppns :+ passthrough_ppn) io.resp.ppn := Mux1H(hitsVec, ppns :+ passthrough_ppn)
io.ptw.req.valid := state === s_request io.ptw.req.valid := state === s_request
@ -169,7 +176,7 @@ class TLB(entries: Int)(implicit edge: TLEdgeOut, p: Parameters) extends CoreMod
state := s_ready state := s_ready
} }
when (io.ptw.invalidate) { when (io.ptw.invalidate || multipleHits) {
valid := 0 valid := 0
} }
} }