Yuan Yao has uploaded this change for review. (
https://gem5-review.googlesource.com/c/public/gem5/+/26343 )
Change subject: mem-ruby: Fix fast-forward when using the backing store.
......................................................................
mem-ruby: Fix fast-forward when using the backing store.
While the up-to-date data may reside in any agent of Ruby's memory
hierarchy,
there's an optional backing store in Ruby that provides a 'correct' view of
the
physical memory. When it is enabled by the user, every Ruby memory access
will
update this global memory view as well upon finishing.
The issue is that Ruby's atomic access, used in fast-forward, does not
currently
access the backing store, leading to data incorrectness. More specifically,
at
the very beginning stage of the simulation, a loader loads the program into
the
backing store using functional accesses. Then the program starts execution
with
fast-forward enabled, using atomic accesses for faster simulation. But
because
atomic access only accesses the real memory hierarchy, the CPU fetches
incorrect
instructions.
The fix is simple. Just make Ruby's atomic access update the backing store
as
well as the real physical memory.
Change-Id: I2541d923e18ea488d383097ca7abd4124e47e59b
---
M src/mem/ruby/system/RubyPort.cc
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/mem/ruby/system/RubyPort.cc
b/src/mem/ruby/system/RubyPort.cc
index 800046e..a6cee05 100644
--- a/src/mem/ruby/system/RubyPort.cc
+++ b/src/mem/ruby/system/RubyPort.cc
@@ -339,7 +339,10 @@
RubySystem *rs = ruby_port->m_ruby_system;
AbstractController *directory =
rs->m_abstract_controls[id.getType()][id.getNum()];
- return directory->recvAtomic(pkt);
+ Tick latency = directory->recvAtomic(pkt);
+ if (access_backing_store)
+ rs->getPhysMem()->access(pkt);
+ return latency;
}
void
--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I2541d923e18ea488d383097ca7abd4124e47e59b
Gerrit-Change-Number: 26343
Gerrit-PatchSet: 1
Gerrit-Owner: Yuan Yao <[email protected]>
Gerrit-MessageType: newchange
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