From 139f635bdeb356011f4fa3f128ecc212b8807d94 Mon Sep 17 00:00:00 2001
From: Samuel Stark <samuel.stark2@arm.com>
Date: Wed, 22 Sep 2021 13:46:32 +0100
Subject: [PATCH] cpu: Allow TLB shootdown requests in the o3 cpu

JIRA: https://gem5.atlassian.net/browse/GEM5-1097

Change-Id: Ie698efd583f592e5564af01c2150fbec969f56a2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56600
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
---
 src/cpu/o3/lsq.cc | 18 +++++++++++-------
 src/cpu/o3/lsq.hh | 19 ++++++++++++-------
 2 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/src/cpu/o3/lsq.cc b/src/cpu/o3/lsq.cc
index c932a9320a..375093a4c9 100644
--- a/src/cpu/o3/lsq.cc
+++ b/src/cpu/o3/lsq.cc
@@ -784,15 +784,16 @@ LSQ::pushRequest(const DynInstPtr& inst, bool isLoad, uint8_t *data,
     assert(!isAtomic || (isAtomic && !needs_burst));
 
     const bool htm_cmd = isLoad && (flags & Request::HTM_CMD);
+    const bool tlbi_cmd = isLoad && (flags & Request::TLBI_CMD);
 
     if (inst->translationStarted()) {
         request = inst->savedRequest;
         assert(request);
     } else {
-        if (htm_cmd) {
+        if (htm_cmd || tlbi_cmd) {
             assert(addr == 0x0lu);
             assert(size == 8);
-            request = new HtmCmdRequest(&thread[tid], inst, flags);
+            request = new UnsquashableDirectRequest(&thread[tid], inst, flags);
         } else if (needs_burst) {
             request = new SplitDataRequest(&thread[tid], inst, isLoad, addr,
                     size, flags, data, res);
@@ -1377,15 +1378,17 @@ LSQ::DcachePort::recvReqRetry()
     lsq->recvReqRetry();
 }
 
-LSQ::HtmCmdRequest::HtmCmdRequest(LSQUnit* port, const DynInstPtr& inst,
-        const Request::Flags& flags_) :
+LSQ::UnsquashableDirectRequest::UnsquashableDirectRequest(
+    LSQUnit* port,
+    const DynInstPtr& inst,
+    const Request::Flags& flags_) :
     SingleDataRequest(port, inst, true, 0x0lu, 8, flags_,
         nullptr, nullptr, nullptr)
 {
 }
 
 void
-LSQ::HtmCmdRequest::initiateTranslation()
+LSQ::UnsquashableDirectRequest::initiateTranslation()
 {
     // Special commands are implemented as loads to avoid significant
     // changes to the cpu and memory interfaces
@@ -1421,8 +1424,9 @@ LSQ::HtmCmdRequest::initiateTranslation()
 }
 
 void
-LSQ::HtmCmdRequest::finish(const Fault &fault, const RequestPtr &req,
-        gem5::ThreadContext* tc, BaseMMU::Mode mode)
+LSQ::UnsquashableDirectRequest::finish(const Fault &fault,
+        const RequestPtr &req, gem5::ThreadContext* tc,
+        BaseMMU::Mode mode)
 {
     panic("unexpected behaviour - finish()");
 }
diff --git a/src/cpu/o3/lsq.hh b/src/cpu/o3/lsq.hh
index 2e9945559a..1d4ecfd353 100644
--- a/src/cpu/o3/lsq.hh
+++ b/src/cpu/o3/lsq.hh
@@ -583,19 +583,24 @@ class LSQ
         virtual std::string name() const { return "SingleDataRequest"; }
     };
 
-    // hardware transactional memory
-    // This class extends SingleDataRequest for the sole purpose
-    // of encapsulating hardware transactional memory command requests
-    class HtmCmdRequest : public SingleDataRequest
+    // This class extends SingleDataRequest for the purpose
+    // of allowing special requests (eg Hardware transactional memory, TLB
+    // shootdowns) to bypass irrelevant system elements like translation &
+    // squashing.
+    class UnsquashableDirectRequest : public SingleDataRequest
     {
       public:
-        HtmCmdRequest(LSQUnit* port, const DynInstPtr& inst,
+        UnsquashableDirectRequest(LSQUnit* port, const DynInstPtr& inst,
                 const Request::Flags& flags_);
-        virtual ~HtmCmdRequest() {}
+        inline virtual ~UnsquashableDirectRequest() {}
         virtual void initiateTranslation();
         virtual void finish(const Fault &fault, const RequestPtr &req,
                 gem5::ThreadContext* tc, BaseMMU::Mode mode);
-        virtual std::string name() const { return "HtmCmdRequest"; }
+        virtual std::string
+        name() const
+        {
+            return "UnsquashableDirectRequest";
+        }
     };
 
     class SplitDataRequest : public LSQRequest