From 78f23ad2dfe2b80ed48900f400d5157e0d92e768 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sa=C3=BAl=20Adserias?=
 <33020671+saul44203@users.noreply.github.com>
Date: Mon, 11 Dec 2023 19:14:40 +0100
Subject: [PATCH] arch-riscv: squash walks with tlb hits in startWalkWrapper

Change-Id: I1bdfd7b2ee02ddee5a2d4c13bafc8c472f555f61
---
 src/arch/riscv/pagetable_walker.cc | 45 ++++++++++++++++++++++++------
 src/arch/riscv/tlb.hh              |  3 +-
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/src/arch/riscv/pagetable_walker.cc b/src/arch/riscv/pagetable_walker.cc
index cbd5bd2b22..3700a48706 100644
--- a/src/arch/riscv/pagetable_walker.cc
+++ b/src/arch/riscv/pagetable_walker.cc
@@ -200,8 +200,19 @@ Walker::startWalkWrapper()
 {
     unsigned num_squashed = 0;
     WalkerState *currState = currStates.front();
+
+    // check if we get a tlb hit to skip the walk
+    Addr vaddr = Addr(sext<VADDR_BITS>(currState->req->getVaddr()));
+    TlbEntry *e = tlb->lookup(vaddr, currState->satp.asid, currState->mode,
+                              true);
+    Fault fault = NoFault;
+    if (e) {
+       fault = tlb->checkPermissions(currState->status, currState->pmode,
+                                     vaddr, currState->mode, e->pte);
+    }
+
     while ((num_squashed < numSquashable) && currState &&
-        currState->translation->squashed()) {
+           (currState->translation->squashed() || (e && fault == NoFault))) {
         currStates.pop_front();
         num_squashed++;
 
@@ -209,9 +220,14 @@ Walker::startWalkWrapper()
             currState->req->getVaddr());
 
         // finish the translation which will delete the translation object
-        currState->translation->finish(
-            std::make_shared<UnimpFault>("Squashed Inst"),
-            currState->req, currState->tc, currState->mode);
+        if (currState->translation->squashed()) {
+            currState->translation->finish(
+                std::make_shared<UnimpFault>("Squashed Inst"),
+                currState->req, currState->tc, currState->mode);
+        } else {
+            tlb->translateTiming(currState->req, currState->tc,
+                                 currState->translation, currState->mode);
+        }
 
         // delete the current request if there are no inflight packets.
         // if there is something in flight, delete when the packets are
@@ -223,13 +239,26 @@ Walker::startWalkWrapper()
         }
 
         // check the next translation request, if it exists
-        if (currStates.size())
+        if (currStates.size()) {
             currState = currStates.front();
-        else
+            vaddr = Addr(sext<VADDR_BITS>(currState->req->getVaddr()));
+            e = tlb->lookup(vaddr, currState->satp.asid, currState->mode,
+                            true);
+            if (e) {
+               fault = tlb->checkPermissions(currState->status,
+                                             currState->pmode, vaddr,
+                                             currState->mode, e->pte);
+            }
+        } else {
             currState = NULL;
+        }
+    }
+    if (currState && !currState->wasStarted()) {
+        if (!e || fault != NoFault)
+            currState->startWalk();
+        else
+            schedule(startWalkWrapperEvent, clockEdge(Cycles(1)));
     }
-    if (currState && !currState->wasStarted())
-        currState->startWalk();
 }
 
 Fault
diff --git a/src/arch/riscv/tlb.hh b/src/arch/riscv/tlb.hh
index f37143dfb7..10a0512c90 100644
--- a/src/arch/riscv/tlb.hh
+++ b/src/arch/riscv/tlb.hh
@@ -134,12 +134,11 @@ class TLB : public BaseTLB
                               BaseMMU::Mode mode) override;
     Fault finalizePhysical(const RequestPtr &req, ThreadContext *tc,
                            BaseMMU::Mode mode) const override;
+    TlbEntry *lookup(Addr vpn, uint16_t asid, BaseMMU::Mode mode, bool hidden);
 
   private:
     uint64_t nextSeq() { return ++lruSeq; }
 
-    TlbEntry *lookup(Addr vpn, uint16_t asid, BaseMMU::Mode mode, bool hidden);
-
     void evictLRU();
     void remove(size_t idx);