From f5fc1006c3d39b3a85c2f00b61caa1703777d7c8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tiago=20M=C3=BCck?= <tiago.muck@arm.com>
Date: Mon, 14 Feb 2022 15:17:38 -0600
Subject: [PATCH] cpu: fix issues with ruby's memtest
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If the size of the address range is smaller than the maximum number
of outstanding requests allowed downstream, the tester will get stuck
trying to find a unique address. This patch adds a check for this
condition and forces the tester to wait for responses before
trying to generate another request.

Change-Id: Ie894a074cc4f8c7ad3d875dc21e8eb4f04562d72
Signed-off-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56811
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/cpu/testers/memtest/memtest.cc | 18 +++++++++++++++++-
 src/cpu/testers/memtest/memtest.hh |  6 ++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/cpu/testers/memtest/memtest.cc b/src/cpu/testers/memtest/memtest.cc
index f229cabd4c..7c256d8642 100644
--- a/src/cpu/testers/memtest/memtest.cc
+++ b/src/cpu/testers/memtest/memtest.cc
@@ -88,6 +88,7 @@ MemTest::MemTest(const Params &p)
       noResponseEvent([this]{ noResponse(); }, name()),
       port("port", *this),
       retryPkt(nullptr),
+      waitResponse(false),
       size(p.size),
       interval(p.interval),
       percentReads(p.percent_reads),
@@ -96,6 +97,7 @@ MemTest::MemTest(const Params &p)
       requestorId(p.system->getRequestorId(this)),
       blockSize(p.system->cacheLineSize()),
       blockAddrMask(blockSize - 1),
+      sizeBlocks(size / blockSize),
       baseAddr1(p.base_addr_1),
       baseAddr2(p.base_addr_2),
       uncacheAddr(p.uncacheable_base_addr),
@@ -191,6 +193,12 @@ MemTest::completeRequest(PacketPtr pkt, bool functional)
         reschedule(noResponseEvent, clockEdge(progressCheck));
     else if (noResponseEvent.scheduled())
         deschedule(noResponseEvent);
+
+    // schedule the next tick
+    if (waitResponse) {
+        waitResponse = false;
+        schedule(tickEvent, clockEdge(interval));
+    }
 }
 MemTest::MemTestStats::MemTestStats(statistics::Group *parent)
       : statistics::Group(parent),
@@ -205,8 +213,9 @@ MemTest::MemTestStats::MemTestStats(statistics::Group *parent)
 void
 MemTest::tick()
 {
-    // we should never tick if we are waiting for a retry
+    // we should never tick if we are waiting for a retry or response
     assert(!retryPkt);
+    assert(!waitResponse);
 
     // create a new request
     unsigned cmd = random_mt.random(0, 100);
@@ -216,6 +225,13 @@ MemTest::tick()
     Request::Flags flags;
     Addr paddr;
 
+    // halt until we clear outstanding requests, otherwise it won't be able to
+    // find a new unique address
+    if (outstandingAddrs.size() >= sizeBlocks) {
+        waitResponse = true;
+        return;
+    }
+
     // generate a unique address
     do {
         unsigned offset = random_mt.random<unsigned>(0, size - 1);
diff --git a/src/cpu/testers/memtest/memtest.hh b/src/cpu/testers/memtest/memtest.hh
index 2e7824e866..2dc1f13dd1 100644
--- a/src/cpu/testers/memtest/memtest.hh
+++ b/src/cpu/testers/memtest/memtest.hh
@@ -120,6 +120,10 @@ class MemTest : public ClockedObject
 
     PacketPtr retryPkt;
 
+    // Set if reached the maximum number of outstanding requests.
+    // Won't tick until a response is received.
+    bool waitResponse;
+
     const unsigned size;
 
     const Cycles interval;
@@ -142,6 +146,8 @@ class MemTest : public ClockedObject
 
     const Addr blockAddrMask;
 
+    const unsigned sizeBlocks;
+
     /**
      * Get the block aligned address.
      *