sim: Add a system-global option to bypass caches

Virtualized CPUs and the fastmem mode of the atomic CPU require direct
access to physical memory. We currently require caches to be disabled
when using them to prevent chaos. This is not ideal when switching
between hardware virutalized CPUs and other CPU models as it would
require a configuration change on each switch. This changeset
introduces a new version of the atomic memory mode,
'atomic_noncaching', where memory accesses are inserted into the
memory system as atomic accesses, but bypass caches.

To make memory mode tests cleaner, the following methods are added to
the System class:

 * isAtomicMode() -- True if the memory mode is 'atomic' or 'direct'.
 * isTimingMode() -- True if the memory mode is 'timing'.
 * bypassCaches() -- True if caches should be bypassed.

The old getMemoryMode() and setMemoryMode() methods should never be
used from the C++ world anymore.

2 files changed, 2 insertions, 2 deletions

diff --git a/src/cpu/simple/atomic.cc b/src/cpu/simple/atomic.cc
index 7a0778961..d7c4190ee 100644
--- a/src/cpu/simple/atomic.cc
+++ b/src/cpu/simple/atomic.cc
@@ -212,7 +212,7 @@ AtomicSimpleCPU::takeOverFrom(BaseCPU *oldCPU)
 void
 AtomicSimpleCPU::verifyMemoryMode() const
 {
-    if (system->getMemoryMode() != Enums::atomic) {
+    if (!system->isAtomicMode()) {
         fatal("The atomic CPU requires the memory system to be in "
               "'atomic' mode.\n");
     }
diff --git a/src/cpu/simple/timing.cc b/src/cpu/simple/timing.cc
index 7423d082c..ab4ea9256 100644
--- a/src/cpu/simple/timing.cc
+++ b/src/cpu/simple/timing.cc
@@ -191,7 +191,7 @@ TimingSimpleCPU::takeOverFrom(BaseCPU *oldCPU)
 void
 TimingSimpleCPU::verifyMemoryMode() const
 {
-    if (system->getMemoryMode() != Enums::timing) {
+    if (!system->isTimingMode()) {
         fatal("The timing CPU requires the memory system to be in "
               "'timing' mode.\n");
     }